40 CFR Part 50 — National Primary and Secondary Ambient Air Quality Standards

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PART 50—NATIONAL PRIMARY AND SECONDARY AMBIENT AIR QUALITY STANDARDS Authority: 42 U.S.C. 7401, et seq. Source: 36 FR 22384, Nov. 25, 1971, unless otherwise noted. § 50.1 Definitions. (a) As used in this part, all terms not defined herein shall have the meaning given them by the Act. (b) Act (c) Agency (d) Administrator (e) Ambient air (f) Reference method (g) Equivalent method (h) Traceable (i) Indian country (j) Exceptional event i.e., (k) Natural event (l) Exceedance with respect to a national ambient air quality standard (m) Prescribed fire (n) Wildfire (o) Wildland (p) High wind dust event (q) High wind threshold (r) Federal land manager [36 FR 22384, Nov. 25, 1971, as amended at 41 FR 11253, Mar. 17, 1976; 48 FR 2529, Jan. 20, 1983; 63 FR 7274, Feb. 12, 1998; 72 FR 13580, Mar. 22, 2007; 81 FR 68276, Oct. 3, 2016] § 50.2 Scope. (a) National primary and secondary ambient air quality standards under section 109 of the Act are set forth in this part. (b) National primary ambient air quality standards define levels of air quality which the Administrator judges are necessary, with an adequate margin of safety, to protect the public health. National secondary ambient air quality standards define levels of air quality which the Administrator judges necessary to protect the public welfare from any known or anticipated adverse effects of a pollutant. Such standards are subject to revision, and additional primary and secondary standards may be promulgated as the Administrator deems necessary to protect the public health and welfare. (c) The promulgation of national primary and secondary ambient air quality standards shall not be considered in any manner to allow significant deterioration of existing air quality in any portion of any State or Indian country. (d) The proposal, promulgation, or revision of national primary and secondary ambient air quality standards shall not prohibit any State or Indian country from establishing ambient air quality standards for that State or area under a tribal CAA program or any portion thereof which are more stringent than the national standards. [36 FR 22384, Nov. 25, 1971, as amended at 63 FR 7274, Feb. 12, 1998] § 50.3 Reference conditions. All measurements of air quality that are expressed as mass per unit volume ( e.g., 2.5 2.5 [89 FR 10365, Dec. 19, 2024] § 50.4 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level of the annual standard is 0.030 parts per million (ppm), not to be exceeded in a calendar year. The annual arithmetic mean shall be rounded to three decimal places (fractional parts equal to or greater than 0.0005 ppm shall be rounded up). (b) The level of the 24-hour standard is 0.14 parts per million (ppm), not to be exceeded more than once per calendar year. The 24-hour averages shall be determined from successive nonoverlapping 24-hour blocks starting at midnight each calendar day and shall be rounded to two decimal places (fractional parts equal to or greater than 0.005 ppm shall be rounded up). (c) Sulfur oxides shall be measured in the ambient air as sulfur dioxide by the reference method described in appendix A to this part or by an equivalent method designated in accordance with part 53 of this chapter. (d) To demonstrate attainment, the annual arithmetic mean and the second-highest 24-hour averages must be based upon hourly data that are at least 75 percent complete in each calendar quarter. A 24-hour block average shall be considered valid if at least 75 percent of the hourly averages for the 24-hour period are available. In the event that only 18, 19, 20, 21, 22, or 23 hourly averages are available, the 24-hour block average shall be computed as the sum of the available hourly averages using 18, 19, etc. as the divisor. If fewer than 18 hourly averages are available, but the 24-hour average would exceed the level of the standard when zeros are substituted for the missing values, subject to the rounding rule of paragraph (b) of this section, then this shall be considered a valid 24-hour average. In this case, the 24-hour block average shall be computed as the sum of the available hourly averages divided by 24. (e) The standards set forth in this section will remain applicable to all areas notwithstanding the promulgation of SO 2 2 2 2 2 2 2 [61 FR 25579, May 22, 1996, as amended at 75 FR 35592, June 22, 2010] § 50.5 National secondary ambient air quality standard for sulfur oxides (sulfur dioxide). (a) The level of the 3-hour standard is 0.5 parts per million (ppm), not to be exceeded more than once per calendar year. The 3-hour averages shall be determined from successive nonoverlapping 3-hour blocks starting at midnight each calendar day and shall be rounded to 1 decimal place (fractional parts equal to or greater than 0.05 ppm shall be rounded up). (b) Sulfur oxides shall be measured in the ambient air as sulfur dioxide by the reference method described in appendix A of this part or by an equivalent method designated in accordance with part 53 of this chapter. (c) To demonstrate attainment, the second-highest 3-hour average must be based upon hourly data that are at least 75 percent complete in each calendar quarter. A 3-hour block average shall be considered valid only if all three hourly averages for the 3-hour period are available. If only one or two hourly averages are available, but the 3-hour average would exceed the level of the standard when zeros are substituted for the missing values, subject to the rounding rule of paragraph (a) of this section, then this shall be considered a valid 3-hour average. In all cases, the 3-hour block average shall be computed as the sum of the hourly averages divided by 3. [61 FR 25580, May 22, 1996] § 50.6 National primary and secondary ambient air quality standards for PM 10 (a) The level of the national primary and secondary 24-hour ambient air quality standards for particulate matter is 150 micrograms per cubic meter (µg/m 3 3 (b) [Reserved] (c) For the purpose of determining attainment of the primary and secondary standards, particulate matter shall be measured in the ambient air as PM 10 (1) A reference method based on appendix J and designated in accordance with part 53 of this chapter, or (2) An equivalent method designated in accordance with part 53 of this chapter. [52 FR 24663, July 1, 1987, as amended at 62 FR 38711, July 18, 1997; 65 FR 80779, Dec. 22, 2000; 71 FR 61224, Oct. 17, 2006] § 50.7 National primary and secondary ambient air quality standards for PM 2.5 (a) The national primary and secondary ambient air quality standards for particulate matter are 15.0 micrograms per cubic meter (µg/m 3 3 2.5 (1) A reference method based on appendix L of this part and designated in accordance with part 53 of this chapter; or (2) An equivalent method designated in accordance with part 53 of this chapter. (b) The annual primary and secondary PM 2.5 (c) The 24-hour primary and secondary PM 2.5 th [62 FR 38711, July 18, 1997, as amended at 69 FR 45595, July 30, 2004] § 50.8 National primary ambient air quality standards for carbon monoxide. (a) The national primary ambient air quality standards for carbon monoxide are: (1) 9 parts per million (10 milligrams per cubic meter) for an 8-hour average concentration not to be exceeded more than once per year and (2) 35 parts per million (40 milligrams per cubic meter) for a 1-hour average concentration not to be exceeded more than once per year. (b) The levels of carbon monoxide in the ambient air shall be measured by: (1) A reference method based on appendix C and designated in accordance with part 53 of this chapter, or (2) An equivalent method designated in accordance with part 53 of this chapter. (c) An 8-hour average shall be considered valid if at least 75 percent of the hourly average for the 8-hour period are available. In the event that only six (or seven) hourly averages are available, the 8-hour average shall be computed on the basis of the hours available using six (or seven) as the divisor. (d) When summarizing data for comparision with the standards, averages shall be stated to one decimal place. Comparison of the data with the levels of the standards in parts per million shall be made in terms of integers with fractional parts of 0.5 or greater rounding up. [50 FR 37501, Sept. 13, 1985] § 50.9 National 1-hour primary and secondary ambient air quality standards for ozone. (a) The level of the national 1-hour primary and secondary ambient air quality standards for ozone measured by a reference method based on appendix D to this part and designated in accordance with part 53 of this chapter, is 0.12 parts per million (235 µg/m 3 3 (b) The 1-hour standards set forth in this section will remain applicable to all areas notwithstanding the promulgation of 8-hour ozone standards under § 50.10. The 1-hour NAAQS set forth in paragraph (a) of this section will no longer apply to an area one year after the effective date of the designation of that area for the 8-hour ozone NAAQS pursuant to section 107 of the Clean Air Act. Area designations and classifications with respect to the 1-hour standards are codified in 40 CFR part 81. [62 FR 38894, July 18, 1997, as amended at 65 FR 45200, July 20, 2000; 68 FR 38163, June 26, 2003, 69 FR 23996, Apr. 30, 2004; 77 FR 28441, May 14, 2012] § 50.10 National 8-hour primary and secondary ambient air quality standards for ozone. (a) The level of the national 8-hour primary and secondary ambient air quality standards for ozone, measured by a reference method based on appendix D to this part and designated in accordance with part 53 of this chapter, is 0.08 parts per million (ppm), daily maximum 8-hour average. (b) The 8-hour primary and secondary ozone ambient air quality standards are met at an ambient air quality monitoring site when the average of the annual fourth-highest daily maximum 8-hour average ozone concentration is less than or equal to 0.08 ppm, as determined in accordance with appendix I to this part. (c) Until the effective date of the final Implementation of the 2008 National Ambient Air Quality Standards for Ozone: State Implementation Plan Requirements Rule (final SIP Requirements Rule) to be codified at 40 CFR 51.1100 et seq., [62 FR 38894, July 18, 1997, as amended at 77 FR 30170, May 21, 2012; 80 FR 12312, Mar. 6, 2015] § 50.11 National primary and secondary ambient air quality standards for oxides of nitrogen (with nitrogen dioxide as the indicator). (a) The level of the national primary annual ambient air quality standard for oxides of nitrogen is 53 parts per billion (ppb, which is 1 part in 1,000,000,000), annual average concentration, measured in the ambient air as nitrogen dioxide. (b) The level of the national primary 1-hour ambient air quality standard for oxides of nitrogen is 100 ppb, 1-hour average concentration, measured in the ambient air as nitrogen dioxide. (c) The level of the national secondary ambient air quality standard for nitrogen dioxide is 0.053 parts per million (100 micrograms per cubic meter), annual arithmetic mean concentration. (d) The levels of the standards shall be measured by: (1) A reference method based on appendix F to this part; or (2) By a Federal equivalent method (FEM) designated in accordance with part 53 of this chapter. (e) The annual primary standard is met when the annual average concentration in a calendar year is less than or equal to 53 ppb, as determined in accordance with appendix S of this part for the annual standard. (f) The 1-hour primary standard is met when the three-year average of the annual 98th percentile of the daily maximum 1-hour average concentration is less than or equal to 100 ppb, as determined in accordance with appendix S of this part for the 1-hour standard. (g) The secondary standard is attained when the annual arithmetic mean concentration in a calendar year is less than or equal to 0.053 ppm, rounded to three decimal places (fractional parts equal to or greater than 0.0005 ppm must be rounded up). To demonstrate attainment, an annual mean must be based upon hourly data that are at least 75 percent complete or upon data derived from manual methods that are at least 75 percent complete for the scheduled sampling days in each calendar quarter. [75 FR 6531, Feb. 9, 2010] § 50.12 National primary and secondary ambient air quality standards for lead. (a) National primary and secondary ambient air quality standards for lead and its compounds, measured as elemental lead by a reference method based on appendix G to this part, or by an equivalent method, are: 1.5 micrograms per cubic meter, maximum arithmetic mean averaged over a calendar quarter. (b) The standards set forth in this section will remain applicable to all areas notwithstanding the promulgation of lead national ambient air quality standards (NAAQS) in § 50.16. The lead NAAQS set forth in this section will no longer apply to an area one year after the effective date of the designation of that area, pursuant to section 107 of the Clean Air Act, for the lead NAAQS set forth in § 50.16; except that for areas designated nonattainment for the lead NAAQS set forth in this section as of the effective date of § 50.16, the lead NAAQS set forth in this section will apply until that area submits, pursuant to section 191 of the Clean Air Act, and EPA approves, an implementation plan providing for attainment and/or maintenance of the lead NAAQS set forth in § 50.16. (Secs. 109, 301(a) Clean Air Act as amended (42 U.S.C. 7409, 7601(a))) [43 FR 46258, Oct. 5, 1978, as amended at 73 FR 67051, Nov. 12, 2008] § 50.13 National primary and secondary ambient air quality standards for PM 2.5 (a) The national primary and secondary ambient air quality standards for particulate matter are 15.0 micrograms per cubic meter (µg/m 3 3 2.5 (1) A reference method based on appendix L of this part and designated in accordance with part 53 of this chapter; or (2) An equivalent method designated in accordance with part 53 of this chapter. (b) The annual primary and secondary PM 2.5 3 (c) The 24-hour primary and secondary PM 2.5 3 (d) Until the effective date of the final Fine Particulate Matter National Ambient Air Quality Standards: State Implementation Plan Requirements rule to be codified at 40 CFR 51.1000 through 51.1016, the 1997 annual PM 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 [71 FR 61224, Oct. 17, 2006, as amended at 81 FR 58149, Aug. 24, 2016] § 50.14 Treatment of air quality monitoring data influenced by exceptional events. (a) Requirements Scope. (A) An action to designate an area, pursuant to Clean Air Act section 107(d)(1), or redesignate an area, pursuant to Clean Air Act section 107(d)(3), for a particular national ambient air quality standard; (B) The assignment or re-assignment of a classification category to a nonattainment area where such classification is based on a comparison of pollutant design values, calculated according to the specific data handling procedures in 40 CFR part 50 for each national ambient air quality standard, to the level of the relevant national ambient air quality standard; (C) A determination regarding whether a nonattainment area has attained the level of the appropriate national ambient air quality standard by its specified deadline; (D) A determination that an area has data for the specific NAAQS, which qualify the area for an attainment date extension under the CAA provisions for the applicable pollutant; (E) A determination under Clean Air Act section 110(k)(5), if based on an area violating a national ambient air quality standard, that the state implementation plan is inadequate under the requirements of Clean Air Act section 110; and (F) Other actions on a case-by-case basis as determined by the Administrator. (ii) A State, federal land manager or other federal agency may request the Administrator to exclude data showing exceedances or violations of any national ambient air quality standard that are directly due to an exceptional event from use in determinations identified in paragraph (a)(1)(i) of this section by demonstrating to the Administrator's satisfaction that such event caused a specific air pollution concentration at a particular air quality monitoring location. (A) For a federal land manager or other federal agency to be eligible to initiate such a request for data exclusion, the federal land manager or other federal agency must: ( 1 ( 2 (B) With regard to such a request, all provisions in this section that are expressed as requirements applying to a State shall, except as noted, be requirements applying to the federal land manager or other federal agency. (C) Provided all provisions in this section are met, the Administrator shall allow a State to submit demonstrations for any regulatory monitor within its jurisdictional bounds, including those operated by federal land managers, other federal agencies and delegated local agencies. (D) Where multiple agencies within a state submit demonstrations for events that meet the requirements of the Exceptional Events Rule, a State submittal shall have primacy for any regulatory monitor within its jurisdictional bounds. (2) A demonstration to justify data exclusion may include any reliable and accurate data, but must specifically address the elements in paragraphs (c)(3)(iv) and (v) of this section. (b) Determinations by the Administrator Generally. (2) Fireworks displays. (3) Prescribed fires. (ii) In addressing the requirements set forth in paragraph (c)(3)(iv)(D) of this section regarding the not reasonably controllable or preventable criterion: (A) With respect to the requirement that a prescribed fire be not reasonably controllable, the State must either certify to the Administrator that it has adopted and is implementing a smoke management program or the State must demonstrate that the burn manager employed appropriate basic smoke management practices identified in Table 1 to § 50.14. Where a burn manager employs appropriate basic smoke management practices, the State may rely on a statement or other documentation provided by the burn manager that he or she employed those practices. If an exceedance or violation of a NAAQS occurs when a prescribed fire is employing an appropriate basic smoke management practices approach, the State and the burn manager must undertake a review of the subject fire, including a review of the basic smoke management practices applied during the subject fire to ensure the protection of air quality and public health and progress towards restoring and/or maintaining a sustainable and resilient wildland ecosystem. If the prescribed fire becomes the subject of an exceptional events demonstration, documentation of the post-burn review must accompany the demonstration. (B) If the State anticipates satisfying the requirements of paragraph (c)(3)(iv)(D) of this section by employing the appropriate basic smoke management practices identified in Table 1 to § 50.14, then: ( 1 ( 2 1 ( 3 2 1 (C) With respect to the requirement that a prescribed fire be not reasonably preventable, the State may rely upon and reference a multi-year land or resource management plan for a wildland area with a stated objective to establish, restore and/or maintain a sustainable and resilient wildland ecosystem and/or to preserve endangered or threatened species through a program of prescribed fire provided that the Administrator determines that there is no compelling evidence to the contrary in the record and the use of prescribed fire in the area has not exceeded the frequency indicated in that plan. (iii) Provided the Administrator determines that there is no compelling evidence to the contrary in the record, in addressing the requirements set forth in paragraph (c)(3)(iv)(E) of this section regarding the human activity unlikely to recur at a particular location criterion for demonstrations involving prescribed fires on wildland, the State must describe the actual frequency with which a burn was conducted, but may rely upon and reference an assessment of the natural fire return interval or the prescribed fire frequency needed to establish, restore and/or maintain a sustainable and resilient wildland ecosystem contained in a multi-year land or resource management plan with a stated objective to establish, restore and/or maintain a sustainable and resilient wildland ecosystem and/or to preserve endangered or threatened species through a program of prescribed fire. Table 1 to § 50.14—Summary of Basic Smoke Management Practices, Benefit Achieved With the BSMP, and When it is Applied a Basic Smoke Management Practice b Benefit achieved with the BSMP When the BSMP is applied—before/during/after the burn Evaluate Smoke Dispersion Conditions Minimize smoke impacts Before, During, After. Monitor Effects on Air Quality Be aware of where the smoke is going and degree it impacts air quality Before, During, After. Record-Keeping/Maintain a Burn/Smoke Journal Retain information about the weather, burn and smoke. If air quality problems occur, documentation helps analyze and address air regulatory issues. Before, During, After. Communication—Public Notification Notify neighbors and those potentially impacted by smoke, especially sensitive receptors Before, During. Consider Emission Reduction Techniques Reducing emissions through mechanisms such as reducing fuel loading can reduce downwind impacts Before, During, After. Share the Airshed—Coordination of Area Burning Coordinate multiple burns in the area to manage exposure of the public to smoke Before, During, After. a b (4) Wildfires. (5) High wind dust events. (ii) The Administrator will consider high wind dust events to be natural events in cases where windblown dust is entirely from natural undisturbed lands in the area or where all anthropogenic sources are reasonably controlled as determined in accordance with paragraph (b)(8) of this section. (iii) The Administrator will accept a high wind threshold of a sustained wind of 25 mph for areas in the States of Arizona, California, Colorado, Kansas, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma, South Dakota, Texas, Utah, and Wyoming provided this value is not contradicted by evidence in the record at the time the State submits a demonstration. In lieu of this threshold, States can identify and use an Administrator-approved alternate area-specific high wind threshold that is more representative of local or regional conditions, if appropriate. (iv) In addressing the requirements set forth in paragraph (c)(3)(iv)(D) of this section regarding the not reasonably preventable criterion, the State shall not be required to provide a case-specific justification for a high wind dust event. (v) With respect to the not reasonably controllable criterion of paragraph (c)(3)(iv)(D) of this section, dust controls on an anthropogenic source shall be considered reasonable in any case in which the controls render the anthropogenic source as resistant to high winds as natural undisturbed lands in the area affected by the high wind dust event. The Administrator may determine lesser controls reasonable on a case-by-case basis. (vi) For large-scale and high-energy high wind dust events, the Administrator will generally consider a demonstration documenting the nature and extent of the event to be sufficient with respect to the not reasonably controllable criterion of paragraph (c)(3)(iv)(D) of this section provided the State provides evidence showing that the event satisfies the following: (A) The event is associated with a dust storm and is the focus of a Dust Storm Warning. (B) The event has sustained winds that are greater than or equal to 40 miles per hour. (C) The event has reduced visibility equal to or less than 0.5 miles. (6) Stratospheric Intrusions. (7) Determinations with respect to event aggregation, multiple national ambient air quality standards for the same pollutant, and exclusion of 24-hour values for particulate matter. (i) Where a State demonstrates to the Administrator's satisfaction that for national ambient air quality standards with averaging or cumulative periods less than or equal to 24 hours the aggregate effect of events occurring on the same day has caused an exceedance or violation, the Administrator shall determine such collective data to satisfy the requirements in paragraph (c)(3)(iv)(B) of this section regarding the clear causal relationship criterion. Where a State demonstrates to the Administrator's satisfaction that for national ambient air quality standards with averaging or cumulative periods longer than 24 hours the aggregate effect of events occurring on different days has caused an exceedance or violation, the Administrator shall determine such collective data to satisfy the requirements in paragraph (c)(3)(iv)(B) of this section regarding the clear causal relationship criterion. (ii) The Administrator shall accept as part of a demonstration for the clear causal relationship in paragraph (c)(3)(iv)(B) of this section with respect to a 24-hour NAAQS, a State's comparison of a 24-hour concentration of any national ambient air quality standard pollutant to the level of a national ambient air quality standard for the same pollutant with a longer averaging period. The Administrator shall also accept as part of a demonstration for the clear causal relationship in paragraph (c)(3)(iv)(B) of this section with respect to a NAAQS with a longer averaging period, a State's comparison of a 24-hour concentration of any national ambient air quality standard pollutant to the level of the national ambient air quality standard for the same pollutant with a longer averaging period, without the State having to demonstrate that the event caused the annual average concentration of the pollutant to exceed the level of the NAAQS with the longer averaging period. (iii) Where a State operates a continuous analyzer that has been designated as a Federal Equivalent Method monitor as defined in 40 CFR 50.1(g) that complies with the monitoring requirements of 40 CFR part 58, Appendix C, and the State believes that collected data have been influenced by an event, in following the process outlined in paragraph (c)(2) of this section, the State shall create an initial event description and flag the associated event-influenced data that have been submitted to the AQS database for the affected monitor. Where a State demonstrates to the Administrator's satisfaction that such data satisfy the requirements in paragraph (c)(3)(iv)(B) of this section regarding the clear causal relationship criterion and otherwise satisfy the requirements of this section, the Administrator shall agree to exclude all data within the affected calendar day(s). (8) Determinations with respect to the not reasonably controllable or preventable criterion. (ii) The Administrator shall determine that an event is not reasonably preventable if the State shows that reasonable measures to prevent the event were applied at the time of the event. (iii) The Administrator shall determine that an event is not reasonably controllable if the State shows that reasonable measures to control the impact of the event on air quality were applied at the time of the event. (iv) The Administrator shall assess the reasonableness of available controls for anthropogenic sources based on information available as of the date of the event. (v) Except where a State, tribal or federal air agency is obligated to revise its state implementation plan, tribal implementation plan, or federal implementation plan, the Administrator shall consider enforceable control measures implemented in accordance with a state implementation plan, tribal implementation plan, or federal implementation plan, approved by the EPA within 5 years of the date of the event, that address the event-related pollutant and all sources necessary to fulfill the requirements of the Clean Air Act for the state implementation plan, tribal implementation plan, or federal implementation plan to be reasonable controls with respect to all anthropogenic sources that have or may have contributed to the monitored exceedance or violation. (vi) Where a State, tribal or federal air agency is obligated to revise its state implementation plan, tribal implementation plan, or federal implementation plan, the deference to enforceable control measures identified in paragraph (b)(8)(v) of this section shall remain only until the due date of the required state implementation plan, tribal implementation plan, or federal implementation plan revisions. However, where an air agency is obligated to revise the enforceable control measures identified in paragraph (b)(8)(v) of this section in its implementation plan as a result of an action pursuant to Clean Air Act section 110(k)(5), the deference, if any, to those enforceable control measures shall be determined on a case-by-case basis. (vii) The Administrator shall not require a State to provide case-specific justification to support the not reasonably controllable or preventable criterion for emissions-generating activity that occurs outside of the State's jurisdictional boundaries within which the concentration at issue was monitored. In the case of a tribe treated as a state under 40 CFR 49.2 with respect to exceptional events requirements, the tribe's jurisdictional boundaries for purposes of requiring or directly implementing emission controls apply. In the case of a federal land manager or other federal agency submitting a demonstration under the requirements of this section, the jurisdictional boundaries that apply are those of the State or the tribe depending on which has jurisdiction over the area where the event has occurred. (viii) In addition to the provisions that apply to specific event types identified in paragraphs (b)(3)(ii) and (b)(5)(i) through (iii) of this section in addressing the requirements set forth in paragraph (c)(3)(iv)(D) of this section regarding the not reasonably controllable or preventable criterion, the State must include the following components: (A) Identification of the natural and anthropogenic sources of emissions causing and contributing to the monitored exceedance or violation, including the contribution from local sources. (B) Identification of the relevant state implementation plan, tribal implementation plan, or federal implementation plan or other enforceable control measures in place for the sources identified in paragraph (b)(8)(vii)(A) of this section and the implementation status of these controls. (C) Evidence of effective implementation and enforcement of the measures identified in paragraph (b)(8)(vii)(B) of this section. (D) The provisions in this paragraph shall not apply if the provisions in paragraph (b)(4), (b)(5)(vi), or (b)(6) of this section apply. (9) Mitigation plans. (ii) The prohibition on placing a concurrence flag in the appropriate field for the data record in the AQS database by the Administrator stated in paragraph (b)(9(i) of this section does not apply to data that are included in an exceptional events demonstration that is: (A) submitted in accordance with paragraph (c)(3) of this section that is also of the type and pollutant that is the focus of the mitigation plan, and (B) submitted within the 2-year period allowed for mitigation plan development as specified in 40 CFR 51.930(b)(3). (c) Schedules and procedures Public notification. (ii) [Reserved] (2) Initial notification of potential exceptional event. (A) The State and the appropriate EPA Regional office shall engage in regular communications to identify those data that have been potentially influenced by an exceptional event, to determine whether the identified data may affect a regulatory determination and to discuss whether the State should develop and submit an exceptional events demonstration according to the requirements in this section; (B) For data that may affect an anticipated regulatory determination or where circumstances otherwise compel the Administrator to prioritize the resulting demonstration, the Administrator shall respond to a State's Initial Notification of Potential Exceptional Event with a due date for demonstration submittal that considers the nature of the event and the anticipated timing of the associated regulatory decision; (C) The Administrator may waive the Initial Notification of Potential Exceptional Event process on a case-by-case basis. (ii) The data shall not be excluded from determinations with respect to exceedances or violations of the national ambient air quality standards unless and until, following the State's submittal of its demonstration pursuant to paragraph (c)(3) of this section and the Administrator's review, the Administrator notifies the State of its concurrence by placing a concurrence flag in the appropriate field for the data record in the AQS database. (iii) [Reserved] (iv) [Reserved] (v) [Reserved] (vi) Table 2 to § 50.14 identifies the submission process for data that will or may influence the initial designation of areas for any new or revised national ambient air quality standard. Table 2 to § 50.14—Schedule for Initial Notification and Demonstration Submission for Data Influenced by Exceptional Events for Use in Initial Area Designations Exceptional events/Regulatory action Condition Exceptional events deadline schedule d (A) Initial Notification deadline for data years 1, 2 and 3. a If state and tribal initial designation recommendations for a new/revised national ambient air quality standard are due August through January, then the Initial Notification deadline will be the July 1 prior to the recommendation deadline. (B) Initial Notification deadline for data years 1, 2 and 3. a If state and tribal recommendations for a new/revised national ambient air quality standard are due February through July, then the Initial Notification deadline will be the January 1 prior to the recommendation deadline. (C) Exceptional events demonstration submittal deadline for data years 1, 2 and 3 a None no later than the later of November 29, 2016 or the date that state and tribal recommendations are due to the Administrator. (D) Initial Notification and exceptional events demonstration submittal deadline for data year 4 b c None by the last day of the month that is 1 year and 7 months after promulgation of a new/revised national ambient air quality standard, unless either paragraph (E) or paragraph (F) applies. (E) Initial Notification and exceptional events demonstration submittal deadline for data year 4 b c If the Administrator follows a 3-year designation schedule the deadline is 2 years and 7 months after promulgation of a new/revised national ambient air quality standard. (F) Initial Notification and exceptional events demonstration submittal deadline for data year 4 b c If the Administrator notifies the state/tribe that it intends to complete the initial area designations process according to a schedule between 2 and 3 years, the deadline is 5 months prior to the date specified for final designations decisions in such Administrator notification. a b c d (3) Submission of demonstrations. (ii) [Reserved] (iii) [Reserved] (iv) The demonstration to justify data exclusion must include: (A) A narrative conceptual model that describes the event(s) causing the exceedance or violation and a discussion of how emissions from the event(s) led to the exceedance or violation at the affected monitor(s); (B) A demonstration that the event affected air quality in such a way that there exists a clear causal relationship between the specific event and the monitored exceedance or violation; (C) Analyses comparing the claimed event-influenced concentration(s) to concentrations at the same monitoring site at other times to support the requirement at paragraph (c)(3)(iv)(B) of this section. The Administrator shall not require a State to prove a specific percentile point in the distribution of data; (D) A demonstration that the event was both not reasonably controllable and not reasonably preventable; and (E) A demonstration that the event was a human activity that is unlikely to recur at a particular location or was a natural event. (v) With the submission of the demonstration containing the elements in paragraph (c)(3)(iv) of this section, the State must: (A) Document that the State followed the public comment process and that the comment period was open for a minimum of 30 days, which could be concurrent with the beginning of the Administrator's initial review period of the associated demonstration provided the State can meet all requirements in this paragraph; (B) Submit the public comments it received along with its demonstration to the Administrator; and (C) Address in the submission to the Administrator those comments disputing or contradicting factual evidence provided in the demonstration. (vi) Where the State has submitted a demonstration according to the requirements of this section after September 30, 2016 and the Administrator has reviewed such demonstration and requested additional evidence to support one of the elements in paragraph (c)(3)(iv) of this section, the State shall have 12 months from the date of the Administrator's request to submit such evidence. At the conclusion of this time, if the State has not submitted the requested additional evidence, the Administrator will notify the State in writing that it considers the demonstration to be inactive and will not pursue additional review of the demonstration. After a 12-month period of inactivity by the State, if a State desires to pursue the inactive demonstration, it must reinitiate its request to exclude associated data by following the process beginning with paragraph (c)(2)(i) of this section. [81 FR 68277, Oct. 3, 2016] § 50.15 National primary and secondary ambient air quality standards for ozone. (a) The level of the national 8-hour primary and secondary ambient air quality standards for ozone (O 3 (b) The 8-hour primary and secondary O 3 3 [73 FR 16511, Mar. 27, 2008] § 50.16 National primary and secondary ambient air quality standards for lead. (a) The national primary and secondary ambient air quality standards for lead (Pb) and its compounds are 0.15 micrograms per cubic meter, arithmetic mean concentration over a 3-month period, measured in the ambient air as Pb either by: (1) A reference method based on appendix G of this part and designated in accordance with part 53 of this chapter or; (2) An equivalent method designated in accordance with part 53 of this chapter. (b) The national primary and secondary ambient air quality standards for Pb are met when the maximum arithmetic 3-month mean concentration for a 3-year period, as determined in accordance with appendix R of this part, is less than or equal to 0.15 micrograms per cubic meter. [73 FR 67052, Nov. 12, 2008] § 50.17 National primary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level of the national primary 1-hour annual ambient air quality standard for oxides of sulfur is 75 parts per billion (ppb, which is 1 part in 1,000,000,000), measured in the ambient air as sulfur dioxide (SO 2 (b) The 1-hour primary standard is met at an ambient air quality monitoring site when the three-year average of the annual (99th percentile) of the daily maximum 1-hour average concentrations is less than or equal to 75 ppb, as determined in accordance with appendix T of this part. (c) The level of the standard shall be measured by a reference method based on appendix A or A-1 of this part, or by a Federal Equivalent Method (FEM) designated in accordance with part 53 of this chapter. [75 FR 35592, June 22, 2010] § 50.18 National primary ambient air quality standards for PM 2.5 (a) The national primary ambient air quality standards for PM 2.5 3 3 2.5 (1) A reference method based on appendix L to this part and designated in accordance with part 53 of this chapter; or (2) An equivalent method designated in accordance with part 53 of this chapter. (b) The primary annual PM 2.5 3 (c) The primary 24-hour PM 2.5 3 [78 FR 3277, Jan. 15, 2013] § 50.19 National primary and secondary ambient air quality standards for ozone. (a) The level of the national 8-hour primary ambient air quality standard for ozone (O 3 (b) The 8-hour primary O 3 3 (c) The level of the national secondary ambient air quality standard for O 3 (d) The 8-hour secondary O 3 3 [80 FR 65452, Oct. 26, 2015] § 50.20 National primary ambient air quality standards for PM 2.5 (a) The national primary ambient air quality standards for PM 2.5 3 3 2.5 (1) A reference method based on appendix L to this part and designated in accordance with part 53 of this chapter; or (2) An equivalent method designated in accordance with part 53 of this chapter. (b) The primary annual PM 2.5 3 (c) The primary 24-hour PM 2.5 3 [89 FR 16380, Mar. 6, 2024] § 50.21 National secondary ambient air quality standards for sulfur oxides (sulfur dioxide). (a) The level of the annual secondary national ambient air quality standard for oxides of sulfur is 10 parts per billion (ppb), measured in the ambient air as sulfur dioxide (SO 2 (b) The annual secondary standard is met when the 3-year average of the annual SO 2 [89 FR 105785, Dec. 27, 2024] Appendix A-1 to Part 50—Reference Measurement Principle and Calibration Procedure for the Measurement of Sulfur Dioxide in the Atmosphere (Ultraviolet Fluorescence Method) 1.0 Applicability 1.1 This ultraviolet fluorescence (UVF) method provides a measurement of the concentration of sulfur dioxide (SO 2 2 2.0 Principle 2.1 This reference method is based on automated measurement of the intensity of the characteristic fluorescence released by SO 2 2 2 2 2.2 The measurement system is calibrated by referencing the instrumental fluorescence measurements to SO 2 2 see 2.3 An analyzer implementing this measurement principle is shown schematically in Figure 1. Designs should include a measurement cell, a UV light source of appropriate wavelength, a UV detector system with appropriate wave length sensitivity, a pump and flow control system for sampling the ambient air and moving it into the measurement cell, sample air conditioning components as necessary to minimize measurement interferences, suitable control and measurement processing capability, and other apparatus as may be necessary. The analyzer must be designed to provide accurate, repeatable, and continuous measurements of SO 2 2.4 Sampling considerations: 2 3.0 Interferences 3.1 The effects of the principal potential interferences may need to be mitigated to meet the interference equivalent requirements of part 53 of this chapter. Aromatic hydrocarbons such as xylene and naphthalene can fluoresce and act as strong positive interferences. These gases can be removed by using a permeation type scrubber (hydrocarbon “kicker”). Nitrogen oxide (NO) in high concentrations can also fluoresce and cause positive interference. Optical filtering can be employed to improve the rejection of interference from high NO. Ozone can absorb UV light given off by the SO 2 2 4.0 Calibration Procedure Atmospheres containing accurately known concentrations of sulfur dioxide are prepared using a compressed gas transfer standard diluted with accurately metered clean air flow rates. 4.1 Apparatus: 2 2 4.1.1 SO 2 4.1.2 Dilution air flow control and measurement devices (or a combined device) capable of regulating and maintaining the air flow rate constant to within ±2 percent and measuring the air flow rate accurate to within ±2, properly calibrated to a NIST-traceable standard. 4.1.3 Mixing chamber, of an inert material such as glass and of proper design to provide thorough mixing of pollutant gas and diluent air streams. 4.1.4 Sampling manifold, constructed of glass, polytetrafluoroethylene (PTFE Teflon TM 4.1.5 Standard gas pressure regulator, of clean stainless steel with a stainless steel diaphragm, suitable for use with a high pressure SO 2 4.1.6 Reagents 4.1.6.1 SO 2 2 2 4.1.6.2 Clean zero air, free of contaminants that could cause a detectable response or a change in sensitivity of the analyzer. Since ultraviolet fluorescence analyzers may be sensitive to aromatic hydrocarbons and O 2 2 2 2 4.2 Procedure 4.2.1 Obtain a suitable calibration apparatus, such as the one shown schematically in Figure 1, and verify that all materials in contact with the pollutant are of glass, Teflon TM 4.2.2 Purge the SO 2 4.2.3 Ensure that there are no leaks in the system and that the flow measuring devices are properly and accurately calibrated under the conditions of use against a reliable volume or flow rate standard such as a soap-bubble meter or a wet-test meter traceable to a NIST standard. All volumetric flow rates should be corrected to the same reference temperature and pressure by using the formula below: Where: F c F m m m P m T m 4.2.4 Allow the SO 2 4.2.5 Adjust the airflow to provide an SO 2 2 4.2.6 Calculate the actual SO 2 Where: C 2 F p 2 F t 4.2.7 When the analyzer response has stabilized, adjust the SO 2 4.2.8 Adjust the flow rate(s) to provide several other SO 2 4.2.9 Plot the analyzer response (vertical or Y-axis) versus SO 2 Note: Additional information on calibration and pollutant standards is provided in Section 12 of Reference 3. 5.0 Frequency of Calibration The frequency of calibration, as well as the number of points necessary to establish the calibration curve and the frequency of other performance checking will vary by analyzer; however, the minimum frequency, acceptance criteria, and subsequent actions are specified in Reference 3, Appendix D: Measurement Quality Objectives and Validation Template for SO 2 6.0 References for SO 2 1. H. Okabe, P. L. Splitstone, and J. J. Ball, “Ambient and Source SO 2 Journal of the Air Control Pollution Association, 2. F. P. Schwarz, H. Okabe, and J. K. Whittaker, “Fluorescence Detection of Sulfur Dioxide in Air at the Parts per Billion Level,” Analytical Chemistry, 3. QA Handbook for Air Pollution Measurement Systems—Volume II. Ambient Air Quality Monitoring Programs. [75 FR 35593, June 22, 2010] Appendix A-2 to Part 50—Reference Method for the Determination of Sulfur Dioxide in the Atmosphere (Pararosaniline Method) 1.0 Applicability. 1.1 This method provides a measurement of the concentration of sulfur dioxide (SO 2 2 2.0 Principle. 2.1 A measured volume of air is bubbled through a solution of 0.04 M potassium tetrachloromercurate (TCM). The SO 2 3 4, 5 ( 6 2 2 3 3.0 Range. 3.1 The lower limit of detection of SO 2 7 2 3 2 3 2 3 8, 9 2 2 3 2 3 4.0 Interferences. 4.1 The effects of the principal potential interferences have been minimized or eliminated in the following manner: Nitrogen oxides by the addition of sulfamic acid,( 10, 11 10, 12 10 10 3 13 5.0 Precision and Accuracy. 5.1 The precision of the analysis is 4.6 percent (at the 95 percent confidence level) based on the analysis of standard sulfite samples.( 10 5.2 Collaborative test results ( 14 2 • The replication error varies linearly with concentration from ±2.5 µg/m 3 3 3 3 • The day-to-day variability within an individual laboratory (repeatability) varies linearly with concentration from ±18.1 µg/m 3 3 3 3 • The day-to-day variability between two or more laboratories (reproducibility) varies linearly with concentration from ±36.9 µg/m 3 3 3 3 • The method has a concentration-dependent bias, which becomes significant at the 95 percent confidence level at the high concentration level. Observed values tend to be lower than the expected SO 2 6.0 Stability. 6.1 By sampling in a controlled temperature environment of 15° ±10 °C, greater than 98.9 percent of the SO 2 15 10 2 2 16 7.0 Apparatus. 7.1 Sampling. 7.1.1 Sample probe: 7.1.2 Absorber—short-term sampling: 7.1.3 Absorber—24-hour sampling: 2 7.1.4 Moisture trap: 7.1.5 Cap seals: 7.1.6 Flow control device: 7.1.7 Flow measurement device: 7.1.8 Membrane particle filter: 7.1.9 Vacuum pump: 7.1.10 Temperature control device: 17 7.1.11 Sampling train container: 7.1.12 Timer: 7.2 Shipping. 7.2.1 Shipping container: 7.3 Analysis. 7.3.1 Spectrophotometer: where: A = absorbance, and T = transmittance (0<≥T<1). A standard wavelength filter traceable to the National Bureau of Standards is used to verify the wavelength calibration according to the procedure enclosed with the filter. The wavelength calibration must be verified upon initial receipt of the instrument and after each 160 hours of normal use or every 6 months, whichever occurs first. 7.3.2 Spectrophotometer cells: 7.3.3 Temperature control device: 7.3.4 Glassware: 7.3.5 TCM waste receptacle: 8.0 Reagents. 8.1 Sampling. 8.1.1 Distilled water: 18 • Place 0.20 mL of potassium permanganate solution (0.316 g/L), 500 mL of distilled water, and 1mL of concentrated sulfuric acid in a chemically resistant glass bottle, stopper the bottle, and allow to stand. • If the permanganate color (pink) does not disappear completely after a period of 1 hour at room temperature, the water is suitable for use. • If the permanganate color does disappear, the water can be purified by redistilling with one crystal each of barium hydroxide and potassium permanganate in an all glass still. 8.1.2 Absorbing reagent Caution: 10 8.2 Analysis. 8.2.1 Sulfamic acid 8.2.2 Formaldehyde 8.2.3 Stock iodine solution 8.2.4 Iodine solution 8.2.5 Starch indicator solution: 8.2.6 1 N hydrochloric acid: 8.2.7 Potassium iodate solution: 8.2.8 Stock sodium thiosulfate solution 2 2 3 2 s where: M = volume of thiosulfate required in mL, and W = weight of potassium iodate in g (recorded weight in Section 8.2.7). 8.2.9 Working sodium thiosulfate titrant T 8.2.10 Standardized sulfite solution for the preparation of working sulfite-TCM solution: 2 2 5 2 3 2 8.2.11 Working sulfite-TCM solution: where: A = volume of thiosulfate titrant required for the blank, mL; B = volume of thiosulfate titrant required for the sample, mL; N T 32,000 = milliequivalent weight of SO 2 25 = volume of standard sulfite solution, mL; and 0.02 = dilution factor. This solution is stable for 30 days if kept at 5 °C. (16) If not kept at 5 °C, prepare fresh daily. 8.2.12 Purified pararosaniline (PRA) stock solution 8.2.12.1 Dye specifications • The dye must have a maximum absorbance at a wavelength of 540 nm when assayed in a buffered solution of 0.1 M sodium acetate-acetic acid; • The absorbance of the reagent blank, which is temperature sensitive (0.015 absorbance unit/ °C), must not exceed 0.170 at 22 °C with a 1-cm optical path length when the blank is prepared according to the specified procedure; • The calibration curve (Section 10.0) must have a slope equal to 0.030 ±0.002 absorbance unit/µg SO 2 8.2.12.2 Preparation of stock PRA solution 10 8.2.12.3 Purification procedure for PRA 1. Place 100 mL each of 1-butanol and 1 N HCl in a large separatory funnel (250-mL) and allow to equilibrate. Note: Certain batches of 1-butanol contain oxidants that create an SO 2 2. Weigh 100 mg of pararosaniline hydrochloride dye (PRA) in a small beaker. Add 50 mL of the equilibrated acid (drain in acid from the bottom of the separatory funnel in 1.) to the beaker and let stand for several minutes. Discard the remaining acid phase in the separatory funnel. 3. To a 125-mL separatory funnel, add 50 mL of the equilibrated 1-butanol (draw the 1-butanol from the top of the separatory funnel in 1.). Transfer the acid solution (from 2.) containing the dye to the funnel and shake carefully to extract. The violet impurity will transfer to the organic phase. 4. Transfer the lower aqueous phase into another separatory funnel, add 20 mL of equilibrated 1-butanol, and extract again. 5. Repeat the extraction procedure with three more 10-mL portions of equilibrated 1-butanol. 6. After the final extraction, filter the acid phase through a cotton plug into a 50-mL volumetric flask and bring to volume with 1 N HCl. This stock reagent will be a yellowish red. 7. To check the purity of the PRA, perform the assay and adjustment of concentration (Section 8.2.12.4) and prepare a reagent blank (Section 11.2); the absorbance of this reagent blank at 540 nm should be less than 0.170 at 22 °C. If the absorbance is greater than 0.170 under these conditions, further extractions should be performed. 8.2.12.4 PRA assay procedure 10 1. Prepare 1 M acetate-acetic acid buffer stock solution with a pH of 4.79 by dissolving 13.61 g of sodium acetate trihydrate in distilled water in a 100-mL volumetric flask. Add 5.70 mL of glacial acetic acid and dilute to volume with distilled water. 2. Pipet 1 mL of the stock PRA solution obtained from the purification process or from a commercial source into a 100-mL volumetric flask and dilute to volume with distilled water. 3. Transfer a 5-mL aliquot of the diluted PRA solution from 2. into a 50-mL volumetric flask. Add 5mL of 1 M acetate-acetic acid buffer solution from 1. and dilute the mixture to volume with distilled water. Let the mixture stand for 1 hour. 4. Measure the absorbance of the above solution at 540 nm with a spectrophotometer against a distilled water reference. Compute the percentage of nominal concentration of PRA by where: A = measured absorbance of the final mixture (absorbance units); W = weight in grams of the PRA dye used in the assay to prepare 50 mL of stock solution (for example, 0.100 g of dye was used to prepare 50 mL of solution in the purification procedure; when obtained from commercial sources, use the stated concentration to compute W; for 98% PRA, W = .098 g.); and K = 21.3 for spectrophotometers having a spectral bandwidth of less than 15 nm and a path length of 1 cm. 8.2.13 Pararosaniline reagent: 9.0 Sampling Procedure. 9.1 General Considerations. 2 3 8,9 9.2 30-Minute and 1-Hour Sampling. 2 9.3 24-Hour Sampling. 9.4 Flow Measurement. 9.4.1 Calibration: 9.4.2 Determination of flow rate at sampling site: where: Q std Q act P b RH = fractional relative humidity of the air being measured; P H 2 O b H 2 O P std b T meter If a barometer is not available, the following equation may be used to determine the barometric pressure: where: H = sampling site elevation above sea level in meters. If the initial flow rate (Q i c i Invalidate the sample if the difference between the initial (Q i f 9.5 Sample Storage and Shipment. 17 10.0 Analytical Calibration. 10.1 Spectrophotometer Cell Matching. 1. Fill all cells with distilled water and designate the one that has the lowest absorbance at 548 nm as the reference. (This reference cell should be marked as such and continually used for this purpose throughout all future analyses.) 2. Zero the spectrophotometer with the reference cell. 3. Determine the absorbance of the remaining cells (A c The corrected absorbance during future analyses using each cell is determining as follows: where: A = corrected absorbance, A obs A c 10.2 Static Calibration Procedure Sulfite-TCM solution Volume of sulfite-TCM solution Volume of TCM, mL Total µg SO 2 Working 4.0 6.0 28.8 Working 3.0 7.0 21.6 Working 2.0 8.0 14.4 Dilute working 10.0 0.0 7.2 Dilute working 5.0 5.0 3.6 0.0 10.0 0.0 *Based on working sulfite-TCM solution concentration of 7.2 µg SO 2 2 To each volumetric flask, add 1 mL 0.6% sulfamic acid (Section 8.2.1), accurately pipet 2 mL 0.2% formaldehyde solution (Section 8.2.2), then add 5 mL pararosaniline solution (Section 8.2.13). Start a laboratory timer that has been set for 30 minutes. Bring all flasks to volume with recently boiled and cooled distilled water and mix thoroughly. The color must be developed (during the 30-minute period) in a temperature environment in the range of 20° to 30 °C, which is controlled to ±1 °C. For increased precision, a constant temperature bath is recommended during the color development step. After 30 minutes, determine the corrected absorbance of each standard at 548 nm against a distilled water reference (Section 10.1). Denote this absorbance as (A). Distilled water is used in the reference cell rather than the reagant blank because of the temperature sensitivity of the reagent blank. Calculate the total micrograms SO 2 where: V TCM/SO C TCM/SO 2 D = dilution factor (D = 1 for the working sulfite-TCM solution; D = 0.1 for the diluted working sulfite-TCM solution). A calibration equation is determined using the method of linear least squares (Section 12.1). The total micrograms SO 2 2 s 10.3 Dynamic Calibration Procedures 2 2 2 19 20 21 2 3 10.3.1 Calibration Option 2A 2 3 2 where: C a 2 3 P r Q d Q p Be sure that the total flow rate of the standard exceeds the flow demand of the sample train, with the excess flow vented at atmospheric pressure. Sample each atmosphere using similar apparatus as shown in Figure 1 and under the same conditions as field sampling ( i.e. 2 2 where: C a 2 3 O s t = sampling time, min; V a V b Add the remaining reagents for color development in the same manner as in Section 10.2 for static solutions. Calculate a calibration equation and a calibration factor (B g 10.3.2 Calibration Option 2B (24-hour samples): Generate a standard atmosphere containing approximately 1,050 µg SO 2 3 2 where: t = sampling time, min; V b C s 2 C a 3 Q s At the completion of sampling, bring the absorber solutions to original volume with distilled water. Pipet a 10-mL portion from each absorber into one of a series of 25-mL volumetric flasks. If the color development steps are not to be started within 12 hours of sampling, store the solutions at 5° ±5 °C. Add the remaining reagents for color development in the same manner as in Section 10.2 for static solutions. Calculate the total µg SO 2 where: V a All other parameters are defined in equation 14. Calculate a calibration equation and a calibration factor (B t 11.0 Sample Preparation and Analysis. 11.1 Sample Preparation. 1. For 30-minute or 1-hour samples: Quantitatively transfer the entire 10 mL amount of absorbing solution to a 25-mL volumetric flask and rinse with a small amount (<5 mL) of distilled water. 2. For 24-hour samples: If the volume of the sample is less than the original 50-mL volume (permanent mark on the absorber), adjust the volume back to the original volume with distilled water to compensate for water lost to evaporation during sampling. If the final volume is greater than the original volume, the volume must be measured using a graduated cylinder. To analyze, pipet 10 mL of the solution into a 25-mL volumetric flask. 11.2 Sample Analysis. 2 1. Allow the sample to stand 20 minutes after the completion of sampling to allow any ozone to decompose (if applicable). 2. To each 25-mL volumetric flask containing reagent blank, sample, or control standard, add 1 mL of 0.6% sulfamic acid (Section 8.2.1) and allow to react for 10 min. 3. Accurately pipet 2 mL of 0.2% formaldehyde solution (Section 8.2.2) and then 5 mL of pararosaniline solution (Section 8.2.13) into each flask. Start a laboratory timer set at 30 minutes. 4. Bring each flask to volume with recently boiled and cooled distilled water and mix thoroughly. 5. During the 30 minutes, the solutions must be in a temperature controlled environment in the range of 20° to 30 °C maintained to ±1 °C. This temperature must also be within 1 °C of that used during calibration. 6. After 30 minutes and before 60 minutes, determine the corrected absorbances (equation 10) of each solution at 548 nm using 1-cm optical path length cells against a distilled water reference (Section 10.1). ( Distilled water is used as a reference instead of the reagent blank because of the sensitivity of the reagent blank to temperature.) 7. Do not allow the colored solution to stand in the cells because a film may be deposited. Clean the cells with isopropyl alcohol after use. 8. The reagent blank must be within 0.03 absorbance units of the intercept of the calibration equation determined in Section 10. 11.3 Absorbance range. 11.4 Reagent disposal. 12.0 Calculations. 12.1 Calibration Slope, Intercept, and Correlation Coefficient. where: y = corrected absorbance, m = slope, absorbance unit/µg SO 2 x = micrograms of SO 2 b = y intercept (absorbance units). The slope (m), intercept (b), and correlation coefficient (r) are calculated as follows: where n is the number of calibration points. A data form (Figure 5) is supplied for easily organizing calibration data when the slope, intercept, and correlation coefficient are calculated by hand. 12.2 Total Sample Volume. where: V std Q i Q f t = total sampling time, min. 12.3 Sulfur Dioxide Concentration. where: A = corrected absorbance of the sample solution, from equation (10); A o B X s g t V a V b V std Data Form [For hand calculations] Calibration point no. Micro- grams So 2 Absor- bance units (x) (y) x 2 xy y 2 1 2 3 4 5 6 Σ x=______ Σ y=______ Σ x 2 2 n=______ (number of pairs of coordinates.) Figure 5. 12.4 Control Standards. Calculate the analyzed micrograms of SO 2 where: C q 2 A = corrected absorbance of the control standard, and A o The difference between the true and analyzed values of the control standards must not be greater than 1 µg. If the difference is greater than 1 µg, the source of the discrepancy must be identified and corrected. 12.5 Conversion of µg/m 3 2 13.0 The TCM absorbing solution and any reagents containing mercury compounds must be treated and disposed of by one of the methods discussed below. Both methods remove greater than 99.99 percent of the mercury. 13.1 Disposal of Mercury-Containing Solutions. 13.2 Method for Forming an Amalgam. 1. Place the waste solution in an uncapped vessel in a hood. 2. For each liter of waste solution, add approximately 10 g of sodium carbonate until neutralization has occurred (NaOH may have to be used). 3. Following neutralization, add 10 g of granular zinc or magnesium. 4. Stir the solution in a hood for 24 hours. Caution must be exercised as hydrogen gas is evolved by this treatment process. 5. After 24 hours, allow the solution to stand without stirring to allow the mercury amalgam (solid black material) to settle to the bottom of the waste receptacle. 6. Upon settling, decant and discard the supernatant liquid. 7. Quantitatively transfer the solid material to a container and allow to dry. 8. The solid material can be sent to a mercury reclaiming plant. It must not be discarded. 13.3 Method Using Aluminum Foil Strips. 1. Place the waste solution in an uncapped vessel in a hood. 2. For each liter of waste solution, add approximately 10 g of aluminum foil strips. If all the aluminum is consumed and no gas is evolved, add an additional 10 g of foil. Repeat until the foil is no longer consumed and allow the gas to evolve for 24 hours. 3. Decant the supernatant liquid and discard. 4. Transfer the elemental mercury that has settled to the bottom of the vessel to a storage container. 5. The mercury can be sent to a mercury reclaiming plant. It must not be discarded. 14.0 References for SO 2 Method. 1. Quality Assurance Handbook for Air Pollution Measurement Systems, Volume I, Principles. EPA-600/9-76-005, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, 1976. 2. Quality Assurance Handbook for Air Pollution Measurement Systems, Volume II, Ambient Air Specific Methods. EPA-600/4-77-027a, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, 1977. 3. Dasqupta, P. K., and K. B. DeCesare. Stability of Sulfur Dioxide in Formaldehyde and Its Anomalous Behavior in Tetrachloromercurate (II). Submitted for publication in Atmospheric Environment, 4. West, P. W., and G. C. Gaeke. Fixation of Sulfur Dioxide as Disulfitomercurate (II) and Subsequent Colorimetric Estimation. Anal. Chem., 28:1816, 1956. 5. Ephraim, F. Inorganic Chemistry. P. C. L. Thorne and E. R. Roberts, Eds., 5th Edition, Interscience, 1948, p. 562. 6. Lyles, G. R., F. B. Dowling, and V. J. Blanchard. Quantitative Determination of Formaldehyde in the Parts Per Hundred Million Concentration Level. J. Air. Poll. Cont. Assoc., Vol. 15(106), 1965. 7. McKee, H. C., R. E. Childers, and O. Saenz, Jr. Collaborative Study of Reference Method for Determination of Sulfur Dioxide in the Atmosphere (Pararosaniline Method). EPA-APTD-0903, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, September 1971. 8. Urone, P., J. B. Evans, and C. M. Noyes. Tracer Techniques in Sulfur—Air Pollution Studies Apparatus and Studies of Sulfur Dioxide Colorimetric and Conductometric Methods. Anal. Chem., 37: 1104, 1965. 9. Bostrom, C. E. The Absorption of Sulfur Dioxide at Low Concentrations (pphm) Studied by an Isotopic Tracer Method. Intern. J. Air Water Poll., 9:333, 1965. 10. Scaringelli, F. P., B. E. Saltzman, and S. A. Frey. Spectrophotometric Determination of Atmospheric Sulfur Dioxide. Anal. Chem., 39: 1709, 1967. 11. Pate, J. B., B. E. Ammons, G. A. Swanson, and J. P. Lodge, Jr. Nitrite Interference in Spectrophotometric Determination of Atmospheric Sulfur Dioxide. Anal. Chem., 37:942, 1965. 12. Zurlo, N., and A. M. Griffini. Measurement of the Sulfur Dioxide Content of the Air in the Presence of Oxides of Nitrogen and Heavy Metals. Medicina Lavoro, 53:330, 1962. 13. Rehme, K. A., and F. P. Scaringelli. Effect of Ammonia on the Spectrophotometric Determination of Atmospheric Concentrations of Sulfur Dioxide. Anal. Chem., 47:2474, 1975. 14. McCoy, R. A., D. E. Camann, and H. C. McKee. Collaborative Study of Reference Method for Determination of Sulfur Dioxide in the Atmosphere (Pararosaniline Method) (24-Hour Sampling). EPA-650/4-74-027, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, December 1973. 15. Fuerst, R. G. Improved Temperature Stability of Sulfur Dioxide Samples Collected by the Federal Reference Method. EPA-600/4-78-018, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, April 1978. 16. Scaringelli, F. P., L. Elfers, D. Norris, and S. Hochheiser. Enhanced Stability of Sulfur Dioxide in Solution. Anal. Chem., 42:1818, 1970. 17. Martin, B. E. Sulfur Dioxide Bubbler Temperature Study. EPA-600/4-77-040, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, August 1977. 18. American Society for Testing and Materials. ASTM Standards, Water; Atmospheric Analysis. Part 23. Philadelphia, PA, October 1968, p. 226. 19. O'Keeffe, A. E., and G. C. Ortman. Primary Standards for Trace Gas Analysis. Anal. Chem., 38:760, 1966. 20. Scaringelli, F. P., S. A. Frey, and B. E. Saltzman. Evaluation of Teflon Permeation Tubes for Use with Sulfur Dioxide. Amer. Ind. Hygiene Assoc. J., 28:260, 1967. 21. Scaringelli, F. P., A. E. O'Keeffe, E. Rosenberg, and J. P. Bell, Preparation of Known Concentrations of Gases and Vapors With Permeation Devices Calibrated Gravimetrically. Anal. Chem., 42:871, 1970. 22. A Procedure for Establishing Traceability of Gas Mixtures to Certain National Bureau of Standards Standard Reference Materials. EPA-600/7-81-010, U.S. Environmental Protection Agency, Environmental Monitoring Systems Laboratory (MD-77), Research Triangle Park, NC 27711, January 1981. [47 FR 54899, Dec. 6, 1982; 48 FR 17355, Apr. 22, 1983. Redesignated at 75 FR 35595, June 22, 2010] Appendix B to Part 50—Reference Method for the Determination of Suspended Particulate Matter in the Atmosphere (High-Volume Method) 1.0 Applicability. 1.1 This method provides a measurement of the mass concentration of total suspended particulate matter (TSP) in ambient air for determining compliance with the primary and secondary national ambient air quality standards for particulate matter as specified in § 50.6 and § 50.7 of this chapter. The measurement process is nondestructive, and the size of the sample collected is usually adequate for subsequent chemical analysis. Quality assurance procedures and guidance are provided in part 58, appendixes A and B, of this chapter and in References 1 and 2. 2.0 Principle. 2.1 An air sampler, properly located at the measurement site, draws a measured quantity of ambient air into a covered housing and through a filter during a 24-hr (nominal) sampling period. The sampler flow rate and the geometry of the shelter favor the collection of particles up to 25-50 µm (aerodynamic diameter), depending on wind speed and direction.( 3 2.2 The filter is weighed (after moisture equilibration) before and after use to determine the net weight (mass) gain. The total volume of air sampled, corrected to EPA standard conditions (25 °C, 760 mm Hg [101 kPa]), is determined from the measured flow rate and the sampling time. The concentration of total suspended particulate matter in the ambient air is computed as the mass of collected particles divided by the volume of air sampled, corrected to standard conditions, and is expressed in micrograms per standard cubic meter (µg/std m 3 3.0 Range. 3.1 The approximate concentration range of the method is 2 to 750 µg/std m 3 3.2 At wind speeds between 1.3 and 4.5 m/sec (3 and 10 mph), the high-volume air sampler has been found to collect particles up to 25 to 50 µm, depending on wind speed and direction.( 3 4.0 Precision. 4.1 Based upon collaborative testing, the relative standard deviation (coefficient of variation) for single analyst precision (repeatability) of the method is 3.0 percent. The corresponding value for interlaboratory precision (reproducibility) is 3.7 percent.( 4 5.0 Accuracy. 5.1 The absolute accuracy of the method is undefined because of the complex nature of atmospheric particulate matter and the difficulty in determining the “true” particulate matter concentration. This method provides a measure of particulate matter concentration suitable for the purpose specified under Section 1.0, Applicability. 6.0 Inherent Sources of Error. 6.1 Airflow variation. *At elevated altitudes, the effectiveness of automatic flow controllers may be reduced because of a reduction in the maximum sampler flow. 6.2 Air volume measurement. 6.3 Loss of volatiles. 5 6.4 Artifact particulate matter. 6 7 6.5 Humidity. 8 6.6 Filter handling. 6.7 Nonsampled particulate matter. 9 6.8 Timing errors. 6.9 Recirculation of sampler exhaust. 10 7.0 Apparatus. (See References 1 and 2 for quality assurance information.) Note: Samplers purchased prior to the effective date of this amendment are not subject to specifications preceded by (†). 7.1 Filter. 7.1.1 Size: 7.1.2 Nominal exposed area: 2 2 7.1.3. Material: 8 7.1.4 Collection efficiency: 7.1.5 Recommended pressure drop range: 3 7.1.6 pH: 11 7.1.7 Integrity: 11 7.1.8 Pinholes: 7.1.9 Tear strength: 7.1.10 Brittleness: 7.2 Sampler. 7.2.1 The sampler shall have suitable means to: a. Hold and seal the filter to the sampler housing. b. Allow the filter to be changed conveniently. c. Preclude leaks that would cause error in the measurement of the air volume passing through the filter. d. (†) (†) See note at beginning of Section 7 of this appendix. 7.2.2 Minimum sample flow rate, heavily loaded filter: 3 3 ‡ These specifications are in actual air volume units; to convert to EPA standard air volume units, multiply the specifications by (P b std b std 7.2.3 Maximum sample flow rate, clean filter: 3 3 7.2.4 Blower Motor: 7.3 Sampler shelter. 7.3.1 The sampler shelter shall: a. Maintain the filter in a horizontal position at least 1 m above the sampler supporting surface so that sample air is drawn downward through the filter. b. Be rectangular in shape with a gabled roof, similar to the design shown in Figure 1. c. Cover and protect the filter and sampler from precipitation and other weather. d. Discharge exhaust air at least 40 cm from the sample air inlet. e. Be designed to minimize the collection of dust from the supporting surface by incorporating a baffle between the exhaust outlet and the supporting surface. 7.3.2 The sampler cover or roof shall overhang the sampler housing somewhat, as shown in Figure 1, and shall be mounted so as to form an air inlet gap between the cover and the sampler housing walls. † † † 7.4 Flow rate measurement devices. 7.4.1 The sampler shall incorporate a flow rate measurement device capable of indicating the total sampler flow rate. Two common types of flow indicators covered in the calibration procedure are (1) an electronic mass flowmeter and (2) an orifice or orifices located in the sample air stream together with a suitable pressure indicator such as a manometer, or aneroid pressure gauge. A pressure recorder may be used with an orifice to provide a continuous record of the flow. Other types of flow indicators (including rotameters) having comparable precision and accuracy are also acceptable. 7.4.2 † The flow rate measurement device must be capable of being calibrated and read in units corresponding to a flow rate which is readable to the nearest 0.02 std m 3 3 7.5 Thermometer, 7.5.1 Range: 7.5.2 Resolution: 7.6 Barometer, 7.6.1 Range: 7.6.2 Resolution: 7.7 Timing/control device. 7.7.1 The timing device must be capable of starting and stopping the sampler to obtain an elapsed run-time of 24 hr ±1 hr (1,440 ±60 min). 7.7.2 Accuracy of time setting: 7.8 Flow rate transfer standard, 7.8.1 Approximate range: 3 7.8.2 Resolution: 3 7.8.3 Reproducibility: 7.8.4 Maximum pressure drop at 1.7 std m 3 2 7.8.5 The flow rate transfer standard must connect without leaks to the inlet of the sampler and measure the flow rate of the total air sample. 7.8.6 The flow rate transfer standard must include a means to vary the sampler flow rate over the range of 1.0 to 1.8 m 3 3 7.8.7 The conventional type of flow transfer standard consists of: An orifice unit with adapter that connects to the inlet of the sampler, a manometer or other device to measure orifice pressure drop, a means to vary the flow through the sampler unit, a thermometer to measure the ambient temperature, and a barometer to measure ambient pressure. Two such devices are shown in Figures 2a and 2b. Figure 2a shows multiple fixed resistance plates, which necessitate disassembly of the unit each time the flow resistance is changed. A preferable design, illustrated in Figure 2b, has a variable flow restriction that can be adjusted externally without disassembly of the unit. Use of a conventional, orifice-type transfer standard is assumed in the calibration procedure (Section 9). However, the use of other types of transfer standards meeting the above specifications, such as the one shown in Figure 2c, may be approved; see the note following Section 9.1. 7.9 Filter conditioning environment 7.9.1 Controlled temperature: 7.9.2 Controlled humidity: 7.10 Analytical balance. 7.10.1 Sensitivity: 7.10.2 Weighing chamber designed to accept an unfolded 20.3 × 25.4 cm (8 × 10 in) filter. 7.11 Area light source, 7.12 Numbering device, 8.0 Procedure. (See References 1 and 2 for quality assurance information.) 8.1 Number each filter, if not already numbered, near its edge with a unique identification number. 8.2 Backlight each filter and inspect for pinholes, particles, and other imperfections; filters with visible imperfections must not be used. 8.3 Equilibrate each filter in the conditioning environment for at least 24-hr. 8.4 Following equilibration, weigh each filter to the nearest milligram and record this tare weight (W i 8.5 Do not bend or fold the filter before collection of the sample. 8.6 Open the shelter and install a numbered, preweighed filter in the sampler, following the sampler manufacturer's instructions. During inclement weather, precautions must be taken while changing filters to prevent damage to the clean filter and loss of sample from or damage to the exposed filter. Filter cassettes that can be loaded and unloaded in the laboratory may be used to minimize this problem (See Section 6.6). 8.7 Close the shelter and run the sampler for at least 5 min to establish run-temperature conditions. 8.8 Record the flow indicator reading and, if needed, the barometric pressure (P 3 3 3 3 3 3 8.9 Record the sampler identification information (filter number, site location or identification number, sample date, and starting time). 8.10 Set the timer to start and stop the sampler such that the sampler runs 24-hrs, from midnight to midnight (local time). 8.11 As soon as practical following the sampling period, run the sampler for at least 5 min to again establish run-temperature conditions. 8.12 Record the flow indicator reading and, if needed, the barometric pressure (P 3 3 3 3 Note: No onsite pressure or temperature measurements are necessary if the sampler flow indicator does not require pressure or temperature corrections (e.g., a mass flowmeter) or if average barometric pressure and seasonal average temperature for the site are incorporated into the sampler calibration (see step 9.3.9). For individual pressure and temperature corrections, the ambient pressure and temperature can be obtained by onsite measurements or from a nearby weather station. Barometric pressure readings obtained from airports must be station pressure, not corrected to sea level, and may need to be corrected for differences in elevation between the sampler site and the airport. For samplers having flow recorders but not constant flow controllers, the average temperature and pressure at the site during the sampling period 8.13 Stop the sampler and carefully remove the filter, following the sampler manufacturer's instructions. Touch only the outer edges of the filter. See the precautions in step 8.6. 8.14 Fold the filter in half lengthwise so that only surfaces with collected particulate matter are in contact and place it in the filter holder (glassine envelope or manila folder). 8.15 Record the ending time or elapsed time on the filter information record, either from the stop set-point time, from an elapsed time indicator, or from a continuous flow record. The sample period must be 1,440 ±60 min. for a valid sample. 8.16 Record on the filter information record any other factors, such as meteorological conditions, construction activity, fires or dust storms, etc., that might be pertinent to the measurement. If the sample is known to be defective, void it at this time. 8.17 Equilibrate the exposed filter in the conditioning environment for at least 24-hrs. 8.18 Immediately after equilibration, reweigh the filter to the nearest milligram and record the gross weight with the filter identification number. See Section 10 for TSP concentration calculations. 9.0 Calibration. 9.1 Calibration of the high volume sampler's flow indicating or control device is necessary to establish traceability of the field measurement to a primary standard via a flow rate transfer standard. Figure 3a illustrates the certification of the flow rate transfer standard and Figure 3b illustrates its use in calibrating a sampler flow indicator. Determination of the corrected flow rate from the sampler flow indicator, illustrated in Figure 3c, is addressed in Section 10.1 Note: The following calibration procedure applies to a conventional orifice-type flow transfer standard and an orifice-type flow indicator in the sampler (the most common types). For samplers using a pressure recorder having a square-root scale, 3 other acceptable calibration procedures are provided in Reference 12. Other types of transfer standards may be used if the manufacturer or user provides an appropriately modified calibration procedure that has been approved by EPA under Section 2.8 of appendix C to part 58 of this chapter. 9.2 Certification of the flow rate transfer standard. 9.2.1 Equipment required: 9.2.2 Connect the flow rate transfer standard to the inlet of the standard volume meter. Connect the manometer to measure the pressure at the inlet of the standard volume meter. Connect the orifice manometer to the pressure tap on the transfer standard. Connect a high-volume air pump (such as a high-volume sampler blower) to the outlet side of the standard volume meter. See Figure 3a. 9.2.3 Check for leaks by temporarily clamping both manometer lines (to avoid fluid loss) and blocking the orifice with a large-diameter rubber stopper, wide cellophane tape, or other suitable means. Start the high-volume air pump and note any change in the standard volume meter reading. The reading should remain constant. If the reading changes, locate any leaks by listening for a whistling sound and/or retightening all connections, making sure that all gaskets are properly installed. 9.2.4 After satisfactorily completing the leak check as described above, unclamp both manometer lines and zero both manometers. 9.2.5 Achieve the appropriate flow rate through the system, either by means of the variable flow resistance in the transfer standard or by varying the voltage to the air pump. (Use of resistance plates as shown in Figure 1a is discouraged because the above leak check must be repeated each time a new resistance plate is installed.) At least five different but constant flow rates, evenly distributed, with at least three in the specified flow rate interval (1.1 to 1.7 m 3 3 9.2.6 Measure and record the certification data on a form similar to the one illustrated in Figure 4 according to the following steps. 9.2.7 Observe the barometric pressure and record as P 1 9.2.8 Read the ambient temperature in the vicinity of the standard volume meter and record it as T 1 9.2.9 Start the blower motor, adjust the flow, and allow the system to run for at least 1 min for a constant motor speed to be attained. 9.2.10 Observe the standard volume meter reading and simultaneously start a stopwatch. Record the initial meter reading (V i 9.2.11 Maintain this constant flow rate until at least 3 m 3 9.2.12 After at least 3 m 3 f 9.2.13 Calculate the volume measured by the standard volume meter at meter conditions of temperature and pressures as V m f i 9.2.14 Correct this volume to standard volume (std m 3 where: V std 3 V m P 1 ΔP = differential pressure at inlet to volume meter, mm Hg or kPa; P std T std T 1 Calculate the standard flow rate (std m 3 where: Q std 3 t = elapsed time, minutes. Record Q std 3 9.2.15 Repeat steps 9.2.9 through 9.2.14 for at least four additional constant flow rates, evenly spaced over the approximate range of 1.0 to 1.8 std m 3 3 9.2.16 For each flow, compute √ΔΔH (P 1 std 1 (column 7a of Figure 4) and plot these value against Q std √ΔΔH (P 1 std 1 = mQ std 3 9.2.17 Recalibrate the transfer standard annually or as required by applicable quality control procedures. (See Reference 2.) 9.3 Calibration of sampler flow indicator. Note: For samplers equipped with a flow controlling device, the flow controller must be disabled to allow flow changes during calibration of the sampler's flow indicator, or the alternate calibration of the flow controller given in 9.4 may be used. For samplers using an orifice-type flow indicator downstream of the motor, do not vary the flow rate by adjusting the voltage or power supplied to the sampler. 9.3.1 A form similar to the one illustrated in Figure 5 should be used to record the calibration data. 9.3.2 Connect the transfer standard to the inlet of the sampler. Connect the orifice manometer to the orifice pressure tap, as illustrated in Figure 3b. Make sure there are no leaks between the orifice unit and the sampler. 9.3.3 Operate the sampler for at least 5 minutes to establish thermal equilibrium prior to the calibration. 9.3.4 Measure and record the ambient temperature, T 2 2 9.3.5 Adjust the variable resistance or, if applicable, insert the appropriate resistance plate (or no plate) to achieve the desired flow rate. 9.3.6 Let the sampler run for at least 2 min to re-establish the run-temperature conditions. Read and record the pressure drop across the orifice (ΔH) and the sampler flow rate indication (I) in the appropriate columns of Figure 5. 9.3.7 Calculate √ΔΔH(P 2 std 2 std std std 2 std 2 std 9.3.8 Repeat steps 9.3.5, 9.3.6, and 9.3.7 for several additional flow rates distributed over a range that includes 1.1 to 1.7 std m 3 9.3.9 Determine the calibration curve by plotting values of the appropriate expression involving I, selected from table 1, against Q std a a a a a a a a a a 9.3.10 Draw the sampler calibration curve or calculate the linear least squares slope (m), intercept (b), and correlation coefficient of the calibration curve: [Expression from table 1]= mQ std 3 9.3.11 For a sampler equipped with a flow controller, the flow controlling mechanism should be re-enabled and set to a flow near the lower flow limit to allow maximum control range. The sample flow rate should be verified at this time with a clean filter installed. Then add two or more filters to the sampler to see if the flow controller maintains a constant flow; this is particularly important at high altitudes where the range of the flow controller may be reduced. 9.4 Alternate calibration of flow-controlled samplers. A flow-controlled sampler may be calibrated solely at its controlled flow rate, provided that previous operating history of the sampler demonstrates that the flow rate is stable and reliable. In this case, the flow indicator may remain uncalibrated but should be used to indicate any relative change between initial and final flows, and the sampler should be recalibrated more often to minimize potential loss of samples because of controller malfunction. 9.4.1 Set the flow controller for a flow near the lower limit of the flow range to allow maximum control range. 9.4.2 Install a clean filter in the sampler and carry out steps 9.3.2, 9.3.3, 9.3.4, 9.3.6, and 9.3.7. 9.4.3 Following calibration, add one or two additional clean filters to the sampler, reconnect the transfer standard, and operate the sampler to verify that the controller maintains the same calibrated flow rate; this is particularly important at high altitudes where the flow control range may be reduced. 10.0 Calculations of TSP Concentration. 10.1 Determine the average sampler flow rate during the sampling period according to either 10.1.1 or 10.1.2 below. 10.1.1 For a sampler without a continuous flow recorder, determine the appropriate expression to be used from table 2 corresponding to the one from table 1 used in step 9.3.9. Using this appropriate expression, determine Q std Q std 1/m ([Appropriate expression from table 2]−b) Similarly, determine Q std std 10.1.2 For a sampler with a continuous flow recorder, determine the average flow rate device reading, I, for the period. Determine the appropriate expression from table 2 corresponding to the one from table 1 used in step 9.3.9. Then using this expression and the average flow rate reading, determine Q std Q std 1/m ([Appropriate expression from table 2]−b) If the trace shows substantial flow change during the sampling period, greater accuracy may be achieved by dividing the sampling period into intervals and calculating an average reading before determining Q std 10.2 Calculate the total air volume sampled as: V − Q std where: V = total air volume sampled, in standard volume units, std m 3 Q std 3 t = sampling time, min. 10.3 Calculate and report the particulate matter concentration as: where: TSP = mass concentration of total suspended particulate matter, µg/std m 3 W i W f V = air volume sampled, converted to standard conditions, std m 3 10 6 10.4 If desired, the actual particulate matter concentration (see Section 2.2) can be calculated as follows: (TSP) a 3 std 3 where: (TSP) a 3 TSP = concentration at standard conditions, µg/std m 3 P 3 P std T 3 11.0 References. 1. Quality Assurance Handbook for Air Pollution Measurement Systems, Volume I, Principles. EPA-600/9-76-005, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, 1976. 2. Quality Assurance Handbook for Air Pollution Measurement Systems, Volume II, Ambient Air Specific Methods. EPA-600/4-77-027a, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, 1977. 3. Wedding, J. B., A. R. McFarland, and J. E. Cernak. Large Particle Collection Characteristics of Ambient Aerosol Samplers. Environ. Sci. Technol. 11: 4. McKee, H. C., et al. Collaborative Testing of Methods to Measure Air Pollutants, I. The High-Volume Method for Suspended Particulate Matter. J. Air Poll. Cont. Assoc., 22 (342), 1972. 5. Clement, R. E., and F. W. Karasek. Sample Composition Changes in Sampling and Analysis of Organic Compounds in Aerosols. The Intern. J. Environ. Anal. Chem., 7:109, 1979. 6. Lee, R. E., Jr., and J. Wagman. A Sampling Anomaly in the Determination of Atmospheric Sulfuric Concentration. Am. Ind. Hygiene Assoc. J., 27:266, 1966. 7. Appel, B. R., et al. Interference Effects in Sampling Particulate Nitrate in Ambient Air. Atmospheric Environment, 13:319, 1979. 8. Tierney, G. P., and W. D. Conner. Hygroscopic Effects on Weight Determinations of Particulates Collected on Glass-Fiber Filters. Am. Ind. Hygiene Assoc. J., 28:363, 1967. 9. Chahal, H. S., and D. J. Romano. High-Volume Sampling Effect of Windborne Particulate Matter Deposited During Idle Periods. J. Air Poll. Cont. Assoc., Vol. 26 (885), 1976. 10. Patterson, R. K. Aerosol Contamination from High-Volume Sampler Exhaust. J. Air Poll. Cont. Assoc., Vol. 30 (169), 1980. 11. EPA Test Procedures for Determining pH and Integrity of High-Volume Air Filters. QAD/M-80.01. Available from the Methods Standardization Branch, Quality Assurance Division, Environmental Monitoring Systems Laboratory (MD-77), U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, 1980. 12. Smith, F., P. S. Wohlschlegel, R. S. C. Rogers, and D. J. Mulligan. Investigation of Flow Rate Calibration Procedures Associated with the High-Volume Method for Determination of Suspended Particulates. EPA-600/4-78-047, U.S. Environmental Protection Agency, Research Triangle Park, NC, June 1978. [47 FR 54912, Dec. 6, 1982; 48 FR 17355, Apr. 22, 1983] Appendix C to Part 50—Measurement Principle and Calibration Procedure for the Measurement of Carbon Monoxide in the Atmosphere (Non-Dispersive Infrared Photometry) 1.0 Applicability 1.1 This non-dispersive infrared photometry (NDIR) Federal Reference Method (FRM) provides measurements of the concentration of carbon monoxide (CO) in ambient air for determining compliance with the primary and secondary National Ambient Air Quality Standards (NAAQS) for CO as specified in § 50.8 of this chapter. The method is applicable to continuous sampling and measurement of ambient CO concentrations suitable for determining 1-hour or longer average measurements. The method may also provide measurements of shorter averaging times, subject to specific analyzer performance limitations. Additional CO monitoring quality assurance procedures and guidance are provided in part 58, appendix A, of this chapter and in reference 1 of this appendix C. 2.0 Measurement Principle 2.1 Measurements of CO in ambient air are based on automated measurement of the absorption of infrared radiation by CO in an ambient air sample drawn into an analyzer employing non-wavelength-dispersive, infrared photometry (NDIR method). Infrared energy from a source in the photometer is passed through a cell containing the air sample to be analyzed, and the quantitative absorption of energy by CO in the sample cell is measured by a suitable detector. The photometer is sensitized specifically to CO by employing CO gas in a filter cell in the optical path, which, when compared to a differential optical path without a CO filter cell, limits the measured absorption to one or more of the characteristic wavelengths at which CO strongly absorbs. However, to meet measurement performance requirements, various optical filters, reference cells, rotating gas filter cells, dual-beam configurations, moisture traps, or other means may also be used to further enhance sensitivity and stability of the photometer and to minimize potential measurement interference from water vapor, carbon dioxide (CO 2 2.2 The measurement system is calibrated by referencing the analyzer's CO measurements to CO concentration standards traceable to a National Institute of Standards and Technology (NIST) primary standard for CO, as described in the associated calibration procedure specified in section 4 of this reference method. 2.3 An analyzer implementing this measurement principle will be considered a reference method only if it has been designated as a reference method in accordance with part 53 of this chapter. 2.4 Sampling considerations. 3.0 Interferences 3.1 The NDIR measurement principle is potentially susceptible to interference from water vapor and CO 2 4.0 Calibration Procedures 4.1 Principle. 4.1.1 Dilution method: 4.1.2 Multiple- cylinder method: 4.1.3 Additional information on calibration may be found in Section 12 of reference 1. 4.2 Apparatus. The major components and typical configurations of the calibration systems for the two calibration methods are shown in Figures 1 and 2. Either system may be made up using common laboratory components, or it may be a commercially manufactured system. In either case, the principal components are as follows: 4.2.1 CO standard gas flow control and measurement devices (or a combined device) capable of regulating and maintaining the standard gas flow rate constant to within ±2 percent and measuring the gas flow rate accurate to within ±2 percent, properly calibrated to a NIST-traceable standard. 4.2.2 For the dilution method (Figure 1), dilution air flow control and measurement devices (or a combined device) capable of regulating and maintaining the air flow rate constant to within ±2 percent and measuring the air flow rate accurate to within ±2 percent, properly calibrated to a NIST-traceable standard. 4.2.3 Standard gas pressure regulator(s) for the standard CO cylinder(s), suitable for use with a high-pressure CO gas cylinder and having a non-reactive diaphragm and internal parts and a suitable delivery pressure. 4.2.4 Mixing chamber for the dilution method of an inert material and of proper design to provide thorough mixing of CO standard gas and diluent air streams. 4.2.5 Output sampling manifold, constructed of an inert material and of sufficient diameter to ensure an insignificant pressure drop at the analyzer connection. The system must have a vent designed to ensure nearly atmospheric pressure at the analyzer connection port and to prevent ambient air from entering the manifold. 4.3 Reagents 4.3.1 CO gas concentration transfer standard(s) of CO in air, containing an appropriate concentration of CO suitable for the selected operating range of the analyzer under calibration and traceable to a NIST standard reference material (SRM). If the CO analyzer has significant sensitivity to CO 2 2 2 2 2 4.3.2 For the dilution method, clean zero air, free of contaminants that could cause a detectable response on or a change in sensitivity of the CO analyzer. The zero air should contain <0.1 ppm CO. 4.4 Procedure Using the Dilution Method 4.4.1 Assemble or obtain a suitable dynamic dilution calibration system such as the one shown schematically in Figure 1. Generally, all calibration gases including zero air must be introduced into the sample inlet of the analyzer. However, if the analyzer has special, approved zero and span inlets and automatic valves to specifically allow introduction of calibration standards at near atmospheric pressure, such inlets may be used for calibration in lieu of the sample inlet. For specific operating instructions, refer to the manufacturer's manual. 4.4.2 Ensure that there are no leaks in the calibration system and that all flowmeters are properly and accurately calibrated, under the conditions of use, if appropriate, against a reliable volume or flow rate standard such as a soap-bubble meter or wet-test meter traceable to a NIST standard. All volumetric flow rates should be corrected to the same temperature and pressure such as 298.15 K (25 °C) and 760 mm Hg (101 kPa), using a correction formula such as the following: Where: F c F m T m P m P m T m 4.4.3 Select the operating range of the CO analyzer to be calibrated. Connect the measurement signal output of the analyzer to an appropriate readout instrument to allow the analyzer's measurement output to be continuously monitored during the calibration. Where possible, this readout instrument should be the same one used to record routine monitoring data, or, at least, an instrument that is as closely representative of that system as feasible. 4.4.4 Connect the inlet of the CO analyzer to the output-sampling manifold of the calibration system. 4.4.5 Adjust the calibration system to deliver zero air to the output manifold. The total air flow must exceed the total demand of the analyzer(s) connected to the output manifold to ensure that no ambient air is pulled into the manifold vent. Allow the analyzer to sample zero air until a stable response is obtained. After the response has stabilized, adjust the analyzer zero reading. 4.4.6 Adjust the zero air flow rate and the CO gas flow rate from the standard CO cylinder to provide a diluted CO concentration of approximately 80 percent of the measurement upper range limit (URL) of the operating range of the analyzer. The total air flow rate must exceed the total demand of the analyzer(s) connected to the output manifold to ensure that no ambient air is pulled into the manifold vent. The exact CO concentration is calculated from: Where: [ CO OUT [ CO STD F CO F D Sample this CO concentration until a stable response is obtained. Adjust the analyzer span control to obtain the desired analyzer response reading equivalent to the calculated standard concentration. If substantial adjustment of the analyzer span control is required, it may be necessary to recheck the zero and span adjustments by repeating steps 4.4.5 and 4.4.6. Record the CO concentration and the analyzer's final response. 4.4.7 Generate several additional concentrations (at least three evenly spaced points across the remaining scale are suggested to verify linearity) by decreasing F CO F D 4.5 Procedure Using the Multiple-Cylinder Method. 4.5.1 Use a multi-cylinder, dynamic calibration system such as the typical one shown in Figure 2. 4.5.2 The flowmeter need not be accurately calibrated, provided the flow in the output manifold can be verified to exceed the analyzer's flow demand. 4.5.3 The various CO calibration concentrations required in Steps 4.4.5, 4.4.6, and 4.4.7 are obtained without dilution by selecting zero air or the appropriate certified standard cylinder. 4.6 Frequency of Calibration. 5.0 Reference 1. QA Handbook for Air Pollution Measurement Systems—Volume II. Ambient Air Quality Monitoring Program. [76 FR 54323, Aug. 31, 2011] Appendix D to Part 50—Reference Measurement Principle and Calibration Procedure for the Measurement of Ozone in the Atmosphere (Chemiluminescence Method) 1.0 Applicability. 1.1 This chemiluminescence method provides reference measurements of the concentration of ozone (O 3 3 3 2.0 Measurement Principle. 2.1 This reference method is based on continuous automated measurement of the intensity of the characteristic chemiluminescence released by the gas phase reaction of O 3 2 4 2 4 2.2 The measurement system is calibrated by referencing the instrumental chemiluminescence measurements to certified O 3 3 −1 −1 −1 −1 2.3 An analyzer implementing this measurement principle is shown schematically in Figure 1. Designs implementing this measurement principle must include: an appropriately designed mixing and measurement cell; a suitable quantitative photometric measurement system with adequate sensitivity and wavelength specificity for O 3 2 4 3 2.4 An analyzer implementing this measurement principle and calibration procedure will be considered a federal reference method (FRM) only if it has been designated as a reference method in accordance with part 53 of this chapter. 2.5 Sampling considerations. 3 3 3 3.0 Interferences. 3.1 Except as described in 3.2 below, the chemiluminescence measurement system is inherently free of significant interferences from other pollutant substances that may be present in ambient air. 3.2 A small sensitivity to variations in the humidity of the sample air is minimized by a sample air dryer. Potential loss of O 3 4.0 Calibration Procedure. 4.1 Principle. 3 3 3 0 3 0 0 Where: α = absorption coefficient of O 3 −1 −1 −1 −1 1, 2, 3, 4, 5, 6, 7, 15 c = O 3 l = optical path length in cm. A stable O 3 3 3 0 The calculated O 3 3 4.2 Applicability. 3 4.3 Apparatus. 3 3 3 3, 3 4.3.1 UV photometer. 0, 3 3 4.3.2 Air flow controllers. 4.3.3 Ozone generator. 3 4.3.4 Output manifold. 4.3.5 Two-way valve. 3 4.3.6 Temperature indicator. 4.3.7 Barometer or pressure indicator. 4.4 Reagents. 4.4.1 Zero air. 3 2 4 3 0 3 3 4.5 Procedure. 4.5.1 General operation. 4.5.2 Preparation. 4.5.2.1 Instruction manual. 4.5.2.2 System check. 4.5.2.3 Linearity. 3 Where: E = linearity error, percent A 1 A 2 R = dilution ratio = flow of original concentration divided by the total flow The linearity error must be less than 5%. Since the accuracy of the measured flow-rates will affect the linearity error as measured this way, the test is not necessarily conclusive. Additional information on verifying linearity is contained in Reference 13. 4.5.2.4 Inter-comparison. 4.5.2.5 Ozone losses. 3 3 4.5.3 Assay of O 3 concentrations. 3 4.5.3.1 Allow the photometer system to warm up and stabilize. 4.5.3.2 Verify that the flow rate through the photometer absorption cell, F, allows the cell to be flushed in a reasonably short period of time (2 liter/min is a typical flow). The precision of the measurements is inversely related to the time required for flushing, since the photometer drift error increases with time. 4.5.3.3 Ensure that the flow rate into the output manifold is at least 1 liter/min greater than the total flow rate required by the photometer and any other flow demand connected to the manifold. 4.5.3.4 Ensure that the flow rate of zero air, Fz, is at least 1 liter/min greater than the flow rate required by the photometer. 4.5.3.5 With zero air flowing in the output manifold, actuate the two-way valve to allow the photometer to sample first the manifold zero air, then Fz. The two photometer readings must be equal (I = I 0 Note: In some commercially available photometers, the operation of the two-way valve and various other operations in section 4.5.3 may be carried out automatically by the photometer. 4.5.3.6 Adjust the O 3 3 4.5.3.7 Actuate the two-way valve to allow the photometer to sample zero air until the absorption cell is thoroughly flushed and record the stable measured value of Io. 4.5.3.8 Actuate the two-way valve to allow the photometer to sample the O 3 4.5.3.9 Record the temperature and pressure of the sample in the photometer absorption cell. (See Reference 13 for guidance.) 4.5.3.10. Calculate the O 3 Where: [O 3 OUT 3 α = absorption coefficient of O 3 −1 −1 l = optical path length, cm T = sample temperature, K P = sample pressure, torr L = correction factor for O 3 3 Note: Some commercial photometers may automatically evaluate all or part of equation 4. It is the operator's responsibility to verify that all of the information required for equation 4 is obtained, either automatically by the photometer or manually. For “automatic” photometers which evaluate the first term of equation 4 based on a linear approximation, a manual correction may be required, particularly at higher O3 levels. See the photometer instruction manual and Reference 13 for guidance. 4.5.3.11 Obtain additional O 3 4.5.4 Certification of transfer standards. 3 4.5.5 Calibration of ozone analyzers. 3 4.5.5.1 Allow sufficient time for the O 3 4.5.5.2 Allow the O 3 3 4.5.5.3 Generate an O 3 3 3 3 4.5.5.4 Adjust the O 3 3 4.5.5.5 Generate additional O 3 3 3 3 3 4.5.5.6 Plot the O 3 3 4.5.5.7 Option 1: 3 3 3 3 3 3 Where: [O 3 OUT 3 FO = flow rate through the O 3 FD = diluent air flow rate, liter/min Note: Additional information on calibration and pollutant standards is provided in Section 12 of Reference 14. 5.0 Frequency of Calibration. 5.1 The frequency of calibration, as well as the number of points necessary to establish the calibration curve, and the frequency of other performance checking will vary by analyzer; however, the minimum frequency, acceptance criteria, and subsequent actions are specified in Appendix D of Reference 14: Measurement Quality Objectives and Validation Templates. The user's quality control program shall provide guidelines for initial establishment of these variables and for subsequent alteration as operational experience is accumulated. Manufacturers of analyzers should include in their instruction/operation manuals information and guidance as to these variables and on other matters of operation, calibration, routine maintenance, and quality control. 6.0 References. 1. E.C.Y. Inn and Y. Tanaka, “Absorption coefficient of Ozone in the Ultraviolet and Visible Regions”, J. Opt. Soc. Am., 43, 870 (1953). 2. A. G. Hearn, “Absorption of Ozone in the Ultraviolet and Visible Regions of the Spectrum”, Proc. Phys. Soc. (London), 78, 932 (1961). 3. W. B. DeMore and O. Raper, “Hartley Band Extinction Coefficients of Ozone in the Gas Phase and in Liquid Nitrogen, Carbon Monoxide, and Argon”, J. Phys. Chem., 68, 412 (1964). 4. M. Griggs, “Absorption Coefficients of Ozone in the Ultraviolet and Visible Regions”, J. Chem. Phys., 49, 857 (1968). 5. K. H. Becker, U. Schurath, and H. Seitz, “Ozone Olefin Reactions in the Gas Phase. 1. Rate Constants and Activation Energies”, Int'l Jour. of Chem. Kinetics, VI, 725 (1974). 6. M. A. A. Clyne and J. A. Coxom, “Kinetic Studies of Oxy-halogen Radical Systems”, Proc. Roy. Soc., A303, 207 (1968). 7. J. W. Simons, R. J. Paur, H. A. Webster, and E. J. Bair, “Ozone Ultraviolet Photolysis. VI. The Ultraviolet Spectrum”, J. Chem. Phys., 59, 1203 (1973). 8. Ollison, W.M.; Crow, W.; Spicer, C.W. “Field testing of new-technology ambient air ozone monitors.” J. Air Waste Manage. Assoc., 63 (7), 855-863 (2013). 9. Parrish, D.D.; Fehsenfeld, F.C. “Methods for gas-phase measurements of ozone, ozone precursors and aerosol precursors.” Atmos. Environ., 34 (12-14), 1921-1957(2000). 10. Ridley, B.A.; Grahek, F.E.; Walega, J.G. “A small, high-sensitivity, medium-response ozone detector suitable for measurements from light aircraft.” J. Atmos. Oceanic Technol., 9 (2), 142-148(1992). 11. Boylan, P., Helmig, D., and Park, J.H. “Characterization and mitigation of water vapor effects in the measurement of ozone by chemiluminescence with nitric oxide.” Atmos. Meas. Tech. 7, 1231-1244 (2014). 12. Transfer Standards for Calibration of Ambient Air Monitoring Analyzers for Ozone, EPA publication number EPA-454/B-13-004, October 2013. EPA, Office of Air Quality Planning and Standards, Research Triangle Park, NC 27711. [Available at www.epa.gov/ttnamti1/files/ambient/qaqc/OzoneTransferStandardGuidance.pdf 13. Technical Assistance Document for the Calibration of Ambient Ozone Monitors, EPA publication number EPA-454/B-22-003, January 2023. 14. QA Handbook for Air Pollution Measurement Systems—Volume II. Ambient Air Quality Monitoring Program.

EPA-454/B-17-001, January 2017. 15. Hodges, J.T., Viallon, J., Brewer, P.J., Drouin, B.J., Gorshelev, V., Janssen, C., Lee, S., Possolo, A., Smith, M.A.H., Walden, and Wielgosz, R.I., Recommendation of a consensus value of the ozone absorption cross-section at 253.65 nm based on a literature review, Metrologia, https://doi.org/10.1088/1681-7575/ab0bdd. 7.0 Figures. Figure 1. Gas-phase chemiluminescence analyzer schematic diagram, where PMT means photomultiplier tube. Figure 2. Schematic diagram of a typical UV photometric calibration system. Figure 3. Schematic diagram of a typical UV photometric calibration system (Option 1). [80 FR 65453, Oct. 26, 2015, as amended at 88 FR 70598, Oct. 12, 2023; 90 FR 4651, Jan. 16, 2025] Appendix E to Part 50 [Reserved] Appendix F to Part 50—Measurement Principle and Calibration Procedure for the Measurement of Nitrogen Dioxide in the Atmosphere (Gas Phase Chemiluminescence) Principle and Applicability 1. Atmospheric concentrations of nitrogen dioxide (NO 2 3 1,2,3 2 4,5,6 2 X 2 2 2 2 2. Sampling considerations. 2.1 Chemiluminescence NO/NO X 2 7 2 2 2 2 2.2 The use of integrating flasks on the sample inlet line of chemiluminescence NO/NO X 2 2 3 2.3 The use of particulate filters on the sample inlet line of chemiluminescence NO/NO X 2 Use of the filter should depend on the analyzer's susceptibility to interference, malfunction, or damage due to particulates. Users are cautioned that particulate matter concentrated on a filter may cause erroneous NO 2 3. An analyzer based on this principle will be considered a reference method only if it has been designated as a reference method in accordance with part 53 of this chapter. Calibration 1. Alternative A 3 Major equipment required: 3 X 2 1.1 Principle. 3 2 8 The quantitative nature of this reaction is such that when the NO concentration is known, the concentration of NO 2 X 2 3 2 2 3 3 9 1.2 Apparatus. 3 1.2.1 Air flow controllers. 1.2.2 NO flow controller. 1.2.3 Air flowmeters. 1.2.4 NO flowmeter. 1.2.5 Pressure regulator for standard NO cylinder. 1.2.6 Ozone generator. 3 2 2 1.2.7 Valve. 1.2.8 Reaction chamber. 3 V RC t R R 1.2.9 Mixing chamber. 1.2.10 Output manifold. 1.3 Reagents. 1.3.1 NO concentration standard. 2 2 2 2 2 2 1.3.2 Zero air. X 2 3 2 1.4 Dynamic parameter specification. 1.4.1 The O 3 0 NO where: P R 3 [NO] RC R [NO] STD F NO 3 F O 3 3 V RC 3 1.4.2 The flow conditions to be used in the GPT system are determined by the following procedure: (a) Determine F T F T (b) Establish [NO] OUT OUT URL 2 (c) Determine F NO (d) Select a convenient or available reaction chamber volume. Initially, a trial V RC 3 (e) Compute FO as (f) Compute t R Verify that t R V RC (g) Compute the diluent air flowrate as where: F D 3 (h) If F O V RC F O F D Note: A dynamic parameter lower than 2.75 ppm-minutes may be used if it can be determined empirically that quantitative reaction of O 3 1.5 Procedure. 1.5.1 Assemble a dynamic calibration system such as the one shown in Figure 1. 1.5.2 Insure that all flowmeters are calibrated under the conditions of use against a reliable standard such as a soap-bubble meter or wet-test meter. All volumetric flowrates should be corrected to 25 °C and 760 mm Hg. A discussion on the calibration of flowmeters is given in reference 13. 1.5.3 Precautions must be taken to remove O 2 2 1.5.4 Select the operating range of the NO/NO X 2 2 X X Note: Some analyzer designs may require identical ranges for NO, NO X 2 1.5.5 Connect the recorder output cable(s) of the NO/NO X 2 1.5.6 Determine the GPT flow conditions required to meet the dynamic parameter specification as indicated in 1.4. 1.5.7 Adjust the diluent air and O 3 X 2 Note: Some analyzers may have separate zero controls for NO, NO X 2 X Offsetting the analyzer zero adjustments to + 5 percent of scale is recommended to facilitate observing negative zero drift. Record the stable zero air responses as Z NO Znox Zno2 1.5.8 Preparation of NO and NO X calibration curves. 1.5.8.1 Adjustment of NO span control. URL where: [NO] OUT Sample this NO concentration until the NO and NO X recorder response (percent scale) = where: URL Note: Some analyzers may have separate span controls for NO, NO X 2 X If substantial adjustment of the NO span control is necessary, it may be necessary to recheck the zero and span adjustments by repeating steps 1.5.7 and 1.5.8.1. Record the NO concentration and the analyzer's NO response. 1.5.8.2 Adjustment of NO X span control. X 2 2 X where: [NO X OUT X [NO 2 IMP 2 Adjust the NO X recorder response (% scale) = Note: If the analyzer has only one span control, the span adjustment is made on the NO channel and no further adjustment is made here for NO X If substantial adjustment of the NO X X X 1.5.8.3 Generate several additional concentrations (at least five evenly spaced points across the remaining scale are suggested to verify linearity) by decreasing F NO D X X X X X URL 1.5.9 Preparation of NO 2 calibration curve. 1.5.9.1 Assuming the NO 2 O D NO URL X orig X X X orig 1.5.9.2 Adjust the O 3 3 2 X rem X rem 1.5.9.3 Calculate the resulting NO 2 where: [NO 2 OUT 2 [NO] orig 3 [NO] rem 3 Adjust the NO 2 recorder response (% scale) = Note: If the analyzer has only one or two span controls, the span adjustments are made on the NO channel or NO and NO X 2 If substantial adjustment of the NO 2 2 2 X 1.5.9.4 Maintaining the same F NO O D 2 2 2 2 X 2 2 2 1.5.10 Determination of converter efficiency. 1.5.10.1 For each NO 2 2 2 where: [NO 2 CONV 2 [NO X orig X 3 [NO X rem X 3 Note: Supplemental information on calibration and other procedures in this method are given in reference 13. Plot [NO 2 CONV 2 OUT C 2. Alternative B 2 Major equipment required: Stable O 3 Chemiluminescence NO/NO X 2 NO concentration standard. NO 2 2.1 Principle. 10 2 2 2 2 X 2 X 2.2 Apparatus. 2 2.2.1 Air flow controllers. 2.2.2 NO flow controller. 2.2.3 Air flowmeters. 2.2.4 NO flowmeter. 2.2.5 Pressure regulator for standard NO cylinder. 2.2.6 Drier. 2 2.2.7 Constant temperature chamber. 2 2.2.8 Temperature measuring device. 2 2.2.9 Valves. 2 2 The valves should be constructed of glass, Teflon ®, or other nonreactive material. 2.2.10 Mixing chamber. 2.2.11 Output manifold. 2.3 Reagents. 2.3.1 Calibration standards. 2 2 2 2 2 2 2 2 2 2 2.3.1.1 NO 2 Concentration standard. 2 2 2.3.1.2 NO Concentration standard. 2 2 2 2 2.3.3 Zero air. 2 X 2 2.4 Procedure. 2.4.1 Assemble the calibration apparatus such as the typical one shown in Figure 2. 2.4.2 Insure that all flowmeters are calibrated under the conditions of use against a reliable standard such as a soap bubble meter or wet-test meter. All volumetric flowrates should be corrected to 25 °C and 760 mm Hg. A discussion on the calibration of flowmeters is given in reference 13. 2.4.3 Install the permeation device in the constant temperature chamber. Provide a small fixed air flow (200-400 scm 3 2 2.4.4 Precautions must be taken to remove O 2 2 (1) Carefully evacuating the regulator, when possible, after the regulator has been connected to the cylinder and before opening the cylinder valve; (2) Thoroughly flushing the regulator and delivery system with NO after opening the cylinder valve; (3) Not removing the regulator from the cylinder between calibrations unless absolutely necessary. Further discussion of these procedures is given in reference 13. 2.4.5 Select the operating range of the NO/NO X 2 2 X X Note: Some analyzer designs may require identical ranges for NO, NO X 2 2.4.6 Connect the recorder output cable(s) of the NO/NO X 2 2.4.7 Switch the valve to vent the flow from the permeation device and adjust the diluent air flowrate, F D X 2 Note: Some analyzers may have separate zero controls for NO, NO X 2 X Offsetting the analyzer zero adjustments to + 5% of scale is recommended to facilitate observing negative zero drift. Record the stable zero air responses as Z NO NO X NO 2 2.4.8 Preparation of NO and NO X calibration curves. 2.4.8.1 Adjustment of NO span control. where: [NO] OUT F NO 3 [NO] STD F D 3 Sample this NO concentration until the NO and NO X recorder response (% scale) = where: URL Note: Some analyzers may have separate span controls for NO, NO X 2 X If substantial adjustment of the NO span control is necessary, it may be necessary to recheck the zero and span adjustments by repeating steps 2.4.7 and 2.4.8.1. Record the NO concentration and the analyzer's NO response. 2.4.8.2 Adjustment of NO X span control. X 2 2 X where: [NO X OUT X [NO 2 IMP 2 Adjust the NO X recorder response (% scale) Note: If the analyzer has only one span control, the span adjustment is made on the NO channel and no further adjustment is made here for NO X If substantial adjustment of the NO X X X 2.4.8.3 Generate several additional concentrations (at least five evenly spaced points across the remaining scale are suggested to verify linearity) by decreasing F NO F D X X X X X 2.4.9 Preparation of NO 2 calibration curve. 2.4.9.1 Remove the NO flow. Assuming the NO 2 2 2.4.9.2 Adjust F D 2 URL 2 2 where: [NO 2 OUT 2 R K 2 2 F p 3 F D 3 Sample this NO 2 X 2 2 recorder response (% scale) Note: If the analyzer has only one or two span controls, the span adjustments are made on the NO channel or NO and NO X 2 If substantial adjustment of the NO 2 2 2 X X X M 2.4.9.3 Adjust F D 2 2 2 2 X 2 2 2 2.4.10 Determination of converter efficiency. 2.4.10.1 Plot [NO X M 2 OUT E C Note: Supplemental information on calibration and other procedures in this method are given in reference 13. 3. Frequency of calibration. References 1. A. Fontijn, A. J. Sabadell, and R. J. Ronco, “Homogeneous Chemiluminescent Measurement of Nitric Oxide with Ozone,” Anal. Chem., 42, 575 (1970). 2. D. H. Stedman, E. E. Daby, F. Stuhl, and H. Niki, “Analysis of Ozone and Nitric Oxide by a Chemiluminiscent Method in Laboratory and Atmospheric Studies of Photochemical Smog,” J. Air Poll. Control Assoc., 22, 260 (1972). 3. B. E. Martin, J. A. Hodgeson, and R. K. Stevens, “Detection of Nitric Oxide Chemiluminescence at Atmospheric Pressure,” Presented at 164th National ACS Meeting, New York City, August 1972. 4. J. A. Hodgeson, K. A. Rehme, B. E. Martin, and R. K. Stevens, “Measurements for Atmospheric Oxides of Nitrogen and Ammonia by Chemiluminescence,” Presented at 1972 APCA Meeting, Miami, FL, June 1972. 5. R. K. Stevens and J. A. Hodgeson, “Applications of Chemiluminescence Reactions to the Measurement of Air Pollutants,” Anal. Chem., 45, 443A (1973). 6. L. P. Breitenbach and M. Shelef, “Development of a Method for the Analysis of NO 2 3 7. A. M. Winer, J. W. Peters, J. P. Smith, and J. N. Pitts, Jr., “Response of Commercial Chemiluminescent NO-NO 2 8. K. A. Rehme, B. E. Martin, and J. A. Hodgeson, Tentative Method for the Calibration of Nitric Oxide, Nitrogen Dioxide, and Ozone Analyzers by Gas Phase Titration,” EPA-R2-73-246, March 1974. 9. J. A. Hodgeson, R. K. Stevens, and B. E. Martin, “A Stable Ozone Source Applicable as a Secondary Standard for Calibration of Atmospheric Monitors,” ISA Transactions, 11, 161 (1972). 10. A. E. O'Keeffe and G. C. Ortman, “Primary Standards for Trace Gas Analysis,” Anal. Chem., 38, 760 (1966). 11. F. P. Scaringelli, A. E. O'Keeffe, E. Rosenberg, and J. P. Bell, “Preparation of Known Concentrations of Gases and Vapors with Permeation Devices Calibrated Gravimetrically,” Anal. Chem., 42, 871 (1970). 12. H. L. Rook, E. E. Hughes, R. S. Fuerst, and J. H. Margeson, “Operation Characteristics of NO 2 13. E. C. Ellis, “Technical Assistance Document for the Chemiluminescence Measurement of Nitrogen Dioxide,” EPA-E600/4-75-003 (Available in draft form from the United States Environmental Protection Agency, Department E (MD-76), Environmental Monitoring and Support Laboratory, Research Triangle Park, NC 27711). 14. A Procedure for Establishing Traceability of Gas Mixtures to Certain National Bureau of Standards Standard Reference Materials. EPA-600/7-81-010, Joint publication by NBS and EPA. Available from the U.S. Environmental Protection Agency, Environmental Monitoring Systems Laboratory (MD-77), Research Triangle Park, NC 27711, May 1981. 15. Quality Assurance Handbook for Air Pollution Measurement Systems, Volume II, Ambient Air Specific Methods. [41 FR 52688, Dec. 1, 1976, as amended at 48 FR 2529, Jan. 20, 1983] Appendix G to Part 50—Reference Method for the Determination of Lead in Total Suspended Particulate Matter 1.0 Scope and Applicability Based on review of the air quality criteria and national ambient air quality standard (NAAQS) for lead (Pb) completed in 2008, the EPA made revisions to the primary and secondary NAAQS for Pb to protect public health and welfare. The EPA revised the level from 1.5 µg/m 3 3 Pb-TSP is collected for 24 hours on a TSP filter as described in Appendix B of part 50, the Reference Method for the Determination of Suspended Particulate Matter in the Atmosphere (High-Volume Method). This method is for the analysis of Pb from TSP filters by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) using a heated ultrasonic bath with nitric acid (HNO 3 3 This method is based on the EPA's Office of Solid Waste (SW-846) Method 6020A—Inductively Coupled Plasma Mass Spectrometry (U.S. EPA, 2007). Wording in certain sections of this method is paraphrased or taken directly from Method 6020A. 1.1 ICP-MS is applicable for the sub-µg/mL (ppb) determination of Pb in a wide variety of matrices. Results reported for monitoring or compliance purposes are calculated in µg/m 3 1.2 Due to variations in the isotopic abundance of Pb, the value for total Pb must be based on the sum of the signal intensities for isotopic masses, 206, 207, and 208. Most instrument software packages are able to sum the primary isotope signal intensities automatically. 1.3 ICP-MS requires the use of an internal standard. 115 165 209 1.4 Use of this method is restricted to use by, or under supervision of, properly trained and experienced laboratory personnel. Requirements include training and experience in inorganic sample preparation, including acid extraction, and also knowledge in the recognition and in the correction of spectral, chemical and physical interference in ICP-MS. 2.0 Summary of Method 2.1 This method describes the acid extraction of Pb in particulate matter collected on glass fiber, quartz, or PTFE ambient air filters with subsequent measurement of Pb by ICP-MS. Estimates of the Method Detection Limit (MDL) or sensitivity of the method are provided in Tables 1, 3 and 5 and determined using Pb-spiked filters or filter strips analyzed in accordance with the guidance provided in 40 CFR 136, Appendix B—Determination and procedures for the Determination of the Method Detection Limit—Revision 1.1. The analytical range of the method is 0.00024 µg/m 3 3 3 2.2 This method includes two extraction methods. In the first method, a solution of HNO 3 3 2.3 Calibration standards and check standards are prepared to matrix match the acid composition of the samples. ICP-MS analysis is then performed. With this method, the samples are first aspirated and the aerosol thus created is transported by a flow of argon gas into the plasma torch. The ions produced ( e.g., + 1 3.0 Definitions Pb—Elemental or ionic lead HNO 3 HCl—Hydrochloric acid ICP-MS—Inductively Coupled Plasma Mass Spectrometer MDL—Method detection limit RSD—Relative standard deviation RPD—Relative percent difference CB—Calibration Blank CAL—Calibration Standard ICB—Initial calibration blank CCB—Continuing calibration blank ICV—Initial calibration verification CCV—Continuing calibration verification LLCV—Lower Level Calibration Verification, serves as the lower level ICV and lower level CCV RB—Reagent blank RBS—Reagent blank spike MSDS—Material Safety Data Sheet NIST—National Institute of Standards and Technology D.I. water—Deionized water SRM—NIST Standard Reference Material CRM—Certified Reference Material EPA—Environmental Protection Agency v/v—Volume to volume ratio 4.0 Interferences 4.1 Reagents, glassware, plasticware, and other sample processing hardware may yield artifacts and/or interferences to sample analysis. If reagent blanks, filter blanks, or quality control blanks yield results above the detection limit, the source of contamination must be identified. All containers and reagents used in the processing of the samples must be checked for contamination prior to sample extraction and analysis. Reagents shall be diluted to match the final concentration of the extracts and analyzed for Pb. Labware shall be rinsed with dilute acid solution and the solution analyzed. Once a reagent or labware article (such as extraction tubes) from a manufacturer has been successfully screened, additional screening is not required unless contamination is suspected. 4.2 Isobaric elemental interferences in ICP-MS are caused by isotopes of different elements forming atomic ions with the same nominal mass-to-charge ratio (m/z) as the species of interest. There are no species found in ambient air that will result in isobaric interference with the three Pb isotopes (206, 207, and 208) being measured. Polyatomic interferences occur when two or more elements combine to form an ion with the same mass-to-charge ratio as the isotope being measured. Pb is not subject to interference from common polyatomic ions and no correction is required. 4.3 The distribution of Pb isotopes is not constant. The analysis of total Pb should be based on the summation of signal intensities for the isotopic masses 206, 207, and 208. In most cases, the instrument software can perform the summation automatically. 4.4 Physical interferences are associated with the sample nebulization and transport processes as well as with ion-transmission efficiencies. Dissolved solids can deposit on the nebulizer tip of a pneumatic nebulizer and on the interface skimmers of the ICP-MS. Nebulization and transport processes can be affected if a matrix component causes a change in surface tension or viscosity. Changes in matrix composition can cause significant signal suppression or enhancement. These interferences are compensated for by use of internal standards. Sample dilution will reduce the effects of high levels of dissolved salts, but calibration standards must be prepared in the extraction medium and diluted accordingly. 4.5 Memory interferences are related to sample transport and result when there is carryover from one sample to the next. Sample carryover can result from sample deposition on the sample and skimmer cones and from incomplete rinsing of the sample solution from the plasma torch and the spray chamber between samples. These memory effects are dependent upon both the analyte being measured and sample matrix and can be minimized through the use of suitable rinse times. 5.0 Health and Safety Cautions 5.1 The toxicity or carcinogenicity of reagents used in this method has not been fully established. Each chemical should be regarded as a potential health hazard and exposure to these compounds should be as low as reasonably achievable. Each laboratory is responsible for maintaining a current file of OSHA regulations regarding the safe handling of the chemicals specified in this method. A reference file of material safety data sheets (MSDSs) should be available to all personnel involved in the chemical analysis. Specifically, concentrated HNO 3 5.2 Concentrated HNO 3 3 3 1. Safety goggles (or safety glasses with side shields), 2. Acid resistant rubber gloves, and 3. A protective garment such as a laboratory apron. HNO 3 It is also essential that an eye wash fountain or eye wash bottle be available during performance of this method. An eye wash bottle has a spout that covers the eye. If acid or any other corrosive gets into the eye, the water in this bottle is squirted onto the eye to wash out the harmful material. Eye washing should be performed with large amounts of water immediately after exposure. Medical help should be sought immediately after washing. If either acid, but especially HNO 3 3 5.3 Pb salts and Pb solutions are toxic. Great care must be taken to ensure that samples and standards are handled properly; wash hands thoroughly after handling. 5.4 Care must be taken when using the ultrasonic bath and hot block digester as they are capable of causing mild burns. Users should refer to the safety guidance provided by the manufacturer of their specific equipment. 5.5 Analytical plasma sources emit radio frequency radiation in addition to intense ultra violet (UV) radiation. Suitable precautions should be taken to protect personnel from such hazards. The inductively coupled plasma should only be viewed with proper eye protection from UV emissions. 6.0 Equipment 6.1 Thermo Scientific X-Series ICP-MS or equivalent. The system must be capable of providing resolution better or equal to 1.0 atomic mass unit (amu) at 10 percent peak height. The system must have a mass range from at least 7 to 240 amu that allows for the application of the internal standard technique. For the measurement of Pb, an instrument with a collision or reaction cell is not required. 6.2 Ultrasonic Extraction Equipment 6.2.1 Heated ultrasonic bath capable of maintaining a temperature of 80 °C; VWR Model 750HT, 240W, or equivalent. Ultrasonic bath must meet the following performance criteria: 1. Cut a strip of aluminum foil almost the width of the tank and double the depth. 2. Turn the ultrasonic bath on and lower the foil into the bath vertically until almost touching the bottom of the tank and hold for 10 seconds. 3. Remove the foil from the tank and observe the distribution of perforations and small pin prick holes. The indentations should be fine and evenly distributed. The even distribution of indentations indicates the ultrasonic bath is acceptable for use. 6.2.2 Laboratory centrifuge, Beckman GS-6, or equivalent. 6.2.3 Vortex mixer, VWR Signature Digital Vortex Mixer, VWR Catalog No. 14005-824, or equivalent. 6.3 Hot block extraction equipment 6.3.1 Hot block digester, SCP Science DigiPrep Model MS, No. 010-500-205 block digester capable of maintaining a temperature of 95 °C, or equivalent. 6.4 Materials and Supplies • Argon gas supply, 99.99 percent purity or better. National Welders Microbulk, or equivalent. • Plastic digestion tubes with threaded caps for extraction and storage, SCP Science DigiTUBE® Item No. 010-500-063, or equivalent. • Disposable polypropylene ribbed watch glasses (for heated block extraction), SCP Science Item No. 010-500-081, or equivalent. • Pipette, Rainin EDP2, 100 µL, ±1 percent accuracy, ≤1 percent RSD (precision), with disposable tips, or equivalent. • Pipette, Rainin EDP2, 1000 µL, ±1 percent accuracy, ≤1 percent RSD (precision), with disposable tips, or equivalent. • Pipette, Rainin EDP2, 1-10 mL, ±1 percent accuracy, ≤1 percent RSD (precision), with disposable tips, or equivalent. • Pipette, Thermo Lab Systems, 5 mL, ±1 percent accuracy, ≤1 percent RSD (precision), with disposable tips, or equivalent. • Plastic tweezer, VWR Catalog No. 89026-420, or equivalent. • Laboratory marker. • Ceramic knife, Kyocera LK-25, and non-metal ruler or other suitable cutting tools for making straight cuts for accurately measured strips. • Blank labels or labeling tape, VWR Catalog No. 36425-045, or equivalent. • Graduated cylinder, 1 L, VWR 89000-260, or equivalent. • Volumetric flask, Class A, 1 L, VWR Catalog No. 89025-778, or equivalent. • Millipore Element deionized water system, or equivalent, capable of generating water with a resistivity of ≥17.9 MΩ-cm). • Disposable syringes, 10-mL, with 0.45 micron filters (must be Pb-free). • Plastic or PTFE wash bottles. • Glassware, Class A—volumetric flasks, pipettes, and graduated cylinders. • Glass fiber, quartz, or PTFE filters from the same filter manufacturer and lot used for sample collection for use in the determination of the MDL and for laboratory blanks. 7.0 Reagents and Standards 7.1 Reagent—or trace metals-grade chemicals must be used in all tests. Unless otherwise indicated, it is intended that all reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society, where such specifications are available. 7.2 Concentrated nitric acid, 67-70 percent, SCP Science Catalog No. 250-037-177, or equivalent. 7.3 Concentrated hydrochloric acid (for the ultrasonic extraction method), 33-36 percent, SCP Science Catalog No. 250-037-175, or equivalent. 7.4 Deionized water—All references to deionized water in the method refer to deionized water with a resistivity ≥17.9 MΩ-cm. 7.5 Standard stock solutions may be commercially purchased for each element or as a multi-element mix. Internal standards may be purchased as a mixed multi-element solution. The manufacturer's expiration date and storage conditions must be adhered to. 7.5.1 Lead standard, 1000 µg/mL, NIST traceable, commercially available with certificate of analysis. High Purity Standards Catalog No. 100028-1, or equivalent. 7.5.2 Indium (In) standard, 1000 µg/mL, NIST traceable, commercially available with certificate of analysis. High Purity Standards Catalog No. 100024-1, or equivalent. 7.5.3 Bismuth (Bi) standard, 1000 µg/mL, NIST traceable, commercially available with certificate of analysis. High Purity Standards Catalog No. 100006-1, or equivalent. 7.5.4 Holmium (Ho) standard, 1000 µg/mL, NIST traceable, commercially available with certificate of analysis. High Purity Standards Catalog No. 100023-1, or equivalent. 7.5.5 Second source lead standard, 1000 µg/mL, NIST traceable, commercially available with certificate of analysis. Must be from a different vendor or lot than the standard described in 7.5.1. Inorganic Ventures Catalog No. CGPB-1, or equivalent. 7.5.6 Standard Reference Materials, NIST SRM 2583, 2586, 2587 or 1648, or equivalent. 5 5 http://www.nist.gov/srm/index.cfm. Note: The In, Bi, and Ho internal standards may also be purchased as 10 µg/mL standards. Calibration standards are prepared by diluting stock standards to the appropriate levels in the same acid concentrations as in the final sample volume. The typical range for calibration standards is 0.001 to 2.00 µg/mL. At a minimum, the curve must contain a blank and five Pb containing calibration standards. The calibration standards are stored at ambient laboratory temperature. Calibration standards must be prepared weekly and verified against a freshly prepared ICV using a NIST-traceable source different from the calibration standards. 7.6 Internal standards may be added to the test solution or by on-line addition. The nominal concentration for an internal standard is 0.010 µg/mL (10 ppb). Bismuth (Bi) or holmium (Ho) are the preferred internal standards for Pb, but indium (In) may be used in the event the sample contains Bi and high recoveries are observed. 7.7 Three laboratory blank solutions are required for analysis: (1) The calibration blank is used in the construction of the calibration curve and as a periodic check of system cleanliness (ICB and CCB); (2) the reagent blank (RB) is carried through the extraction process to assess possible contamination; and (3) the rinse blank is run between samples to clean the sample introduction system. If RBs or laboratory blanks yield results above the detection limit, the source of contamination must be identified. Screening of labware and reagents is addressed in Section 4.1. 7.7.1 The calibration blank is prepared in the same acid matrix as the calibration standards and samples and contains all internal standards used in the analysis. 7.7.2 The RB contains all reagents used in the extraction and is carried through the extraction procedure at the same time as the samples. 7.7.3 The rinse blank is a solution of 1 to 2 percent HNO 3 7.7.4 The EPA currently provides glass fiber, quartz, and PTFE filters to air monitoring agencies as requested annually. As part of the procurement process, these filters are tested for acceptance by the EPA. The current acceptance criteria for glass fiber and quartz filters is 15 µg per filter or 0.0075 µg/m 3 3 2 3 3 3 7.7.5 If filters are not provided by the EPA for sample collection and analysis, filter lot blanks should be analyzed for Pb content. For large filter lots (>500 filters), randomly select 20 to 30 filters from the lot and analyze the filter or filter strips for Pb. For smaller filter lots, a lesser number of filters can be analyzed. Glass, quartz and PTFE filters must not have levels of Pb above the criteria specified in section 7.7.4 and, therefore, blank correction should not be performed. If acceptance testing shows levels of Pb above the criteria in Section 7.7.4, corrective action must be taken to reduce the levels before proceeding. 7.8 The Initial Calibration Verification (ICV), Lower Level Calibration Verification (LLCV), and Continuing Calibration Verification (CCV) solutions are prepared from a different Pb source than the calibration curve standards and at a concentration that is either at or below the midpoint on the calibration curve, but within the calibration range. Both are prepared in the same acid matrix as the calibration standards. Note that the same solution may be used for both the ICV and CCV. The ICV/CCV and LLCV solutions must be prepared fresh daily. 7.9 Tuning Solution. Prepare a tuning solution according to the instrument manufacturer's recommendations. This solution will be used to verify the mass calibration and resolution of the instrument. 8.0 Quality Control (QC) 8.1 Standard QC practices shall be employed to assess the validity of the data generated, including: MDL, RB, duplicate samples, spiked samples, serial dilutions, ICV, CCV, LLCV, ICB, CCB, and SRMs/CRMs. 8.2 MDLs must be calculated in accordance with 40 CFR part 136, Appendix B. RBs with low-level standard spikes are used to estimate the MDL. The low-level standard spike is added to at least 7 individual filter strips and then carried through the entire extraction procedure. This will result in at least 7 individual samples to be used for the MDL. The recommended range for spiking the strips is 1 to 5 times the estimated MDL. 8.3 For each batch of samples, one RB and one reagent blank spike (RBS) that is spiked at the same level as the sample spike (see Section 8.6) must be prepared and carried throughout the entire process. The results of the RB must be below 0.001 µg/mL. The recovery for the RBS must be within ±20 percent of the expected value. If the RB yields a result above 0.001 µg/mL, the source of contamination must be identified and the extraction and analysis repeated. Reagents and labware must be suspected as sources of contamination. Screening of reagents and labware is addressed in Section 4.1. 8.4 Any samples that exceed the highest calibration standard must be diluted and rerun so that the concentration falls within the curve. The minimum dilution will be 1 to 5 with matrix matched acid solution. 8.5 The internal standard response must be monitored during the analysis. If the internal standard response falls below 70 percent or rises above 120 percent of expected due to possible matrix effects, the sample must be diluted and reanalyzed. The minimum dilution will be 1 to 5 with matrix matched acid solution. If the first dilution does not correct the problem, additional dilutions must be run until the internal standard falls within the specified range. 8.6 For every batch of samples prepared, there must be one duplicate and one spike sample prepared. The spike added is to be at a level that falls within the calibration curve, normally the midpoint of the curve. The initial plus duplicate sample must yield a relative percent difference ≤20 percent. The spike must be within ±20 percent of the expected value. 8.7 For each batch of samples, one extract must be diluted five-fold and analyzed. The corrected dilution result must be within ±10 percent of the undiluted result. The sample chosen for the serial dilution shall have a concentration at or above 10X the lowest standard in the curve to ensure the diluted value falls within the curve. If the serial dilution fails, chemical or physical interference should be suspected. 8.8 ICB, ICV, LLCV, CCB and CCV samples are to be run as shown in the following table. Sample Frequency Performance specification ICB Prior to first sample Less than 0.001 µg/mL. ICV Prior to first sample Within 90 to 110 percent of the expected value. LLCV Daily, before first sample and after last sample ±10 percent of the expected value. CCB After every 10 extracted samples Less than 0.001 µg/mL. CCV After every 10 extracted samples Within 90-110 percent of the expected value. If any of these QC samples fails to meet specifications, the source of the unacceptable performance must be determined, the problem corrected, and any samples not bracketed by passing QC samples must be reanalyzed. 8.9 For each batch of samples, one certified reference material (CRM) must be combined with a blank filter strip and carried through the entire extraction procedure. The result must be within ±10 percent of the expected value. 8.10 For each run, a LLCV must be analyzed. The LLCV must be prepared at a concentration not more than three times the lowest calibration standard and at a concentration not used in the calibration curve. The LLCV is used to assess performance at the low end of the curve. If the LLCV fails (±10 percent of the expected value) the run must be terminated, the problem corrected, the instrument recalibrated, and the analysis repeated. 8.11 Pipettes used for volumetric transfer must have the calibration checked at least once every 6 months and pass ±1 percent accuracy and ≤1 percent RSD (precision) based on five replicate readings. The pipettes must be checked weekly for accuracy with a single replicate. Any pipette that does not meet ±1 percent accuracy on the weekly check must be removed from service, repaired, and pass a full calibration check before use. 8.12 Samples with physical deformities are not quantitatively analyzable. The analyst should visually check filters prior to proceeding with preparation for holes, tears, or non-uniform deposit which would prevent representative sampling. Document any deformities and qualify the data with flags appropriately. Care must be taken to protect filters from contamination. Filters must be kept covered prior to sample preparation. 9.0 ICP MS Calibration Follow the instrument manufacturer's instructions for the routine maintenance, cleaning, and ignition procedures for the specific ICP-MS instrument being used. 9.1 Ignite the plasma and wait for at least one half hour for the instrument to warm up before beginning any pre-analysis steps. 9.2 For the Thermo X-Series with Xt cones, aspirate a 10 ng/mL tuning solution containing In, Bi, and Ce (Cerium). Monitor the intensities of In, Bi, Ce, and CeO (Cerium oxide) and adjust the instrument settings to achieve the highest In and Bi counts while minimizing the CeO/Ce oxide ratio. For other instruments, follow the manufacturer's recommended practice. Tune to meet the instrument manufacturer's specifications. After tuning, place the sample aspiration probe into a 2 percent HNO 3 9.3 Aspirate a 5 ng/mL solution containing Co, In, and Bi to perform a daily instrument stability check. Run 10 replicates of the solution. The percent RSD for the replicates must be less than 3 percent at all masses. If the percent RSD is greater than 3 percent, the sample introduction system, pump tubing, and tune should be examined, and the analysis repeated. Place the sample aspiration probe into a 2 percent HNO 3 9.4 Load the calibration standards in the autosampler and analyze using the same method parameters that will be used to analyze samples. The curve must include one blank and at least 5 Pb-containing calibration standards. The correlation coefficient must be at least 0.998 for the curve to be accepted. The lowest standard must recover ±15 percent of the expected value and the remaining standards must recover ±10 percent of the expected value to be accepted. 9.5 Immediately after the calibration curve is completed, analyze an ICV and an ICB. The ICV must be prepared from a different source of Pb than the calibration standards. The ICV must recover 90-110 percent of the expected value for the run to continue. The ICB must be less than 0.001 µg/mL. If either the ICV or the ICB fails, the run must be terminated, the problem identified and corrected, and the analysis re-started. 9.6 A LLCV, CCV and a CCB must be run after the ICV and ICB. A CCV and CCB must be run at a frequency of not less than every 10 extracted samples. A typical analytical run sequence would be: Calibration blank, Calibration standards, ICV, ICB, LLCV, CCV, CCB, Extracts 1-10, CCV, CCB, Extracts 11-20, CCV, CCB, Extracts 21-30, CCV, CCB, LLCV, CCV, CCB. Extracts are any field sample or QC samples that have been carried through the extraction process. The CCV solution is prepared from a different source than the calibration standards and may be the same as the ICV solution. The LLCV must be within ±10 percent of expected value. The CCV value must be within ±10 percent of expected for the run to continue. The CCB must be less than 0.001 µg/mL. If either the CCV, LLCV, or CCB fails, the run must be terminated, the problem identified and corrected, and the analysis re-started from the last passing CCV/LLCV/CCB set. 9.7 A LLCV, CCV, and CCB set must be run at the end of the analysis. The LLCV must be within ±30 percent of expected value. If either the CCV, LLCV, or CCB fails, the run must be terminated, the problem identified and corrected, and the analysis re-started from the last passing CCV/LLCV/CCB set. 10.0 Heated Ultrasonic Filter Strip Extraction All plasticware ( e.g., 3 10.1 Sample Preparation—Heated Ultrasonic Bath 10.1.1 Extraction solution (1.03M HNO 3 3 10.1.2 Use a ceramic knife and non-metal ruler, or other cutting device that will not contaminate the filter with Pb. Cut a 3/4 10.1.3 Using plastic tweezers, roll the filter strip up in a coil and place the rolled strip in the bottom of a labeled 50 mL extraction tube. In a fume hood, add 15.00 ±0.15 mL of the extraction solution (see Section 10.1.1) using a calibrated mechanical pipette. Ensure that the extraction solution completely covers the filter strip. 10.1.4 Loosely cap the 50 mL extraction tube and place it upright in a plastic rack. When all samples have been prepared, place the racks in an uncovered heated ultrasonic water bath that has been preheated to 80 ±5 °C and ensure that the water level in the ultrasonic is above the level of the extraction solution in the tubes but well below the level of the extraction tube caps to avoid contamination. Start the ultrasonic bath and allow the unit to run for 1 hour ±5 minutes at 80 ±5 °C. 10.1.5 Remove the rack(s) from the ultrasonic bath and allow the racks to cool. 10.1.6 Add 25.00 ±0.25 mL of D.I. water with a calibrated mechanical pipette to bring the sample to a final volume of 40.0 ±0.4 mL. Tightly cap the tubes, and vortex mix or shake vigorously. Place the extraction tubes in an appropriate holder and centrifuge for 20 minutes at 2500 revolutions per minute (RPM). CAUTION—Make sure that the centrifuge holder has a flat bottom to support the flat bottomed extraction tubes. 10.1.7 Pour an aliquot of the solution into an autosampler vial for ICP-MS analysis to avoid the potential for contamination. Do not pipette an aliquot of solution into the autosampler vial. 10.1.8 Decant the extract to a clean tube, cap tightly, and store the sample extract at ambient laboratory temperature. Extracts may be stored for up to 6 months from the date of extraction. 10.2 47 mm PTFE Filter Extraction—Heated Ultrasonic Bath 10.2.1 Extraction solution (1.03M HNO 3 3 10.2.2 Using plastic tweezers, bend the PTFE filter into a U-shape and insert the filter into a labeled 50 mL extraction tube with the particle loaded side facing the center of the tube. Gently push the filter to the bottom of the extraction tube. In a fume hood, add 25.00 ±0.15 mL of the extraction solution (see Section 10.2.1) using a calibrated mechanical pipette. Ensure that the extraction solution completely covers the filter. 10.2.3 Loosely cap the 50 mL extraction tube and place it upright in a plastic rack. When all samples have been prepared, place the racks in an uncovered heated ultrasonic water bath that has been preheated to 80 ±5 °C and ensure that the water level in the ultrasonic is above the level of the extraction solution in the tubes, but well below the level of the extraction tube caps to avoid contamination. Start the ultrasonic bath and allow the unit to run for 1 hour ±5 minutes at 80 ±5 °C. 10.2.4 Remove the rack(s) from the ultrasonic bath and allow the racks to cool. 10.2.5 Add 25.00 ±0.25 mL of D.I. water with a calibrated mechanical pipette to bring the sample to a final volume of 50.0 ±0.4 mL. Tightly cap the tubes, and vortex mix or shake vigorously. Allow samples to stand for one hour to allow complete diffusion of the extracted Pb. The sample is now ready for analysis. Note: Although PTFE filters have only been extracted using the ultrasonic extraction procedure in the development of this FRM, PTFE filters are inert and have very low Pb content. No issues are expected with the extraction of PTFE filters using the heated block digestion method. However, prior to using PTFE filters in the heated block extraction method, extraction method performance test using CRMs must be done to confirm performance (see Section 8.9). 11.0 Hot Block Filter Strip Extraction All plasticware ( e.g., 3 11.1 Sample Preparation—Hot Block Digestion 11.1.1 Extraction solution (1:19, v/v HNO 3 3 11.1.2 Use a ceramic knife and non-metal ruler, or other cutting device that will not contaminate the filter with Pb. Cut a 1-inch × 8-inch strip from the glass fiber or quartz filter. Cut a strip from the edge of the filter where it has been folded along the 10-inch side at least 1 inch from the right or left side to avoid the un-sampled area covered by the filter holder. The filters must be carefully handled to avoid dislodging particle deposits. 11.1.3 Using plastic tweezers, roll the filter strip up in a coil and place the rolled strip in the bottom of a labeled 50 mL extraction tube. In a fume hood, add 20.0 ±0.15 mL of the extraction solution (see Section 11.1.1) using a calibrated mechanical pipette. Ensure that the extraction solution completely covers the filter strip. 11.1.4 Place the extraction tube in the heated block digester and cover with a disposable polyethylene ribbed watch glass. Heat at 95 ±5 °C for 1 hour and ensure that the sample does not evaporate to dryness. For proper heating, adjust the temperature control of the hot block such that an uncovered vessel containing 50 mL of water placed in the center of the hot block can be maintained at a temperature approximately, but no higher than 85C. Once the vessel is covered with a ribbed watch glass, the temperature of the water will increase to approximately 95 °C. 11.1.5 Remove the rack(s) from the heated block digester and allow the samples to cool. 11.1.6 Bring the samples to a final volume of 50 mL with D.I. water. Tightly cap the tubes, and vortex mix or shake vigorously for at least 5 seconds. Set aside (with the filter strip in the tube) for at least 30 minutes to allow the HNO 3 11.1.7 Shake thoroughly (with the filter strip in the digestion tube) and let settle for at least one hour. The sample is now ready for analysis. 12.0 Measurement Procedure 12.1 Follow the instrument manufacturer's startup procedures for the ICP-MS. 12.2 Set instrument parameters to the appropriate operating conditions as presented in the instrument manufacturer's operating manual and allow the instrument to warm up for at least 30 minutes. 12.3 Calibrate the instrument per Section 9.0 of this method. 12.4 Verify the instrument is suitable for analysis as defined in Sections 9.2 and 9.3. 12.5 As directed in Section 8.0 of this method, analyze an ICV and ICB immediately after the calibration curve followed by a LLCV, then CCV and CCB. The acceptance requirements for these parameters are presented in Section 8.8. 12.6 Analyze a CCV and a CCB after every 10 extracted samples. 12.7 Analyze a LLCV, CCV and CCB at the end of the analysis. 12.8 A typical sample run will include field samples, field sample duplicates, spiked field sample extracts, serially diluted samples, the set of QC samples listed in Section 8.8 above, and one or more CRMs or SRMs. 12.9 Any samples that exceed the highest standard in the calibration curve must be diluted and reanalyzed so that the diluted concentration falls within the calibration curve. 13.0 Results 13.1 The filter results must be initially reported in µg/mL as analyzed. Any additional dilutions must be accounted for. The internal standard recoveries must be included in the result calculation; this is done by the ICP-MS software for most commercially-available instruments. Final results should be reported in µg Pb/m 3 C = ((µg Pb/mL * Vf * A)* D))/Vs Where: C = Concentration, µg Pb/m 3 µg Pb/mL = Lead concentration in solution Vf = Total extraction solution volume A = Area correction; 3/4 2 2 D = dilution factor (if required) Vs = Actual volume of air sampled The calculation assumes the use of a standard 8-inch × 10-inch TSP filter which has a sampled area of 9-inch × 7-inch (63.0 in 2 1/2 3/4 3/4 2 2 14.0 Method Performance Information in this section is an example of typical performance results achieved by this method. Actual performance must be demonstrated by each individual laboratory and instrument. 14.1 Performance data have been collected to estimate MDLs for this method. MDLs were determined in accordance with 40 CFR 136, Appendix B. MDLs were estimated for glass fiber, quartz, and PTFE filters using seven reagent/filter blank solutions spiked with low level Pb at three times the estimated MDL of 0.001 µg/mL. Tables 1, 3, and 5 shows the MDLs estimated using both the ultrasonic and hot block extraction methods for glass fiber and quartz filters and the ultrasonic method for PTFE filters. The MDLs are well below the EPA requirement of five percent of the current Pb NAAQS or 0.0075 µg/m 3 14.2 Extraction method recovery tests with glass fiber and quartz filter strips, and PTFE filters spiked with NIST SRMs were performed using the ultrasonic/HNO 3 Table 1—Method Detection Limits Determined by Analysis of Reagent/Glass Fiber Filter Blanks Spiked With Low-level Pb Solution Ultrasonic Hotblock µg/m 3 µg/m 3 n = 1 0.0000702 0.000533 n = 2 0.0000715 0.000482 n = 3 0.0000611 0.000509 n = 4 0.0000587 0.000427 n = 5 0.0000608 0.000449 n = 6 0.0000607 0.000539 n = 7 0.0000616 0.000481 Average 0.0000635 0.000489 Standard Deviation 0.0000051 0.000042 MDL** 0.0000161 0.000131 * Assumes 2000 m 3 ** MDL is 3.143 times the standard deviation of the results for seven sample replicates analyzed. Table 2—Recoveries of Lead From NIST SRMs Spiked Onto Glass Fiber Filters Extraction method Recovery, ICP-MS, (percent) NIST 1547 plant NIST 2709 soil NIST 2583 dust NIST 2582 paint Ultrasonic Bath 100 ±4 98 ±1 103 ±8 101 ±0 Block Digestion 92 ±7 98 ±3 103 ±4 94 ±4 Table 3—Method Detection Limits Determined by Analysis of Reagent/Quartz Filter Blanks Spiked With Low-level Pb Solution Ultrasonic Hotblock µg/m 3 µg/m 3 n = 1 0.000533 0.000274 n = 2 0.000552 0.000271 n = 3 0.000534 0.000281 n = 4 0.000684 0.000269 n = 5 0.000532 0.000278 n = 6 0.000532 0.000272 n = 7 0.000552 0.000261 Average 0.000560 0.000272 Standard Deviation 0.000055 0.000007 MDL** 0.000174 0.000021 * Assumes 2000 m 3 ** MDL is 3.143 times the standard deviation of the results for seven sample replicates analyzed. Table 4—Recoveries of Lead From NIST SRMs Spiked Onto Quartz Fiber Filters Extraction method Recovery, ICP-MS, (percent) NIST 1547 plant NIST 2709 soil NIST 2583 dust NIST 2582 paint Ultrasonic Bath 101 ±6 95 ±1 91 ±5 93 ±1 Block Digestion 106 ±3 104 ±3 92 ±6 95 ±2 Table 5—Method Detection Limits Determined by Analysis of Reagent/PTFE Filter Blanks Spiked With Low-Level Pb Solution Ultrasonic µg/m 3 n = 1 0.001775 n = 2 0.001812 n = 3 0.001773 n = 4 0.001792 n = 5 0.001712 n = 6 0.001767 n = 7 0.001778 Average 0.001773 Standard Deviation 0.000031 MDL** 0.000097 * Assumes 24 m 3 ** MDL is 3.143 times the standard deviation of the results for seven sample replicates analyzed. Table 6—Recoveries of Lead From NIST SRMs Spiked Onto PTFE Filters Extraction method Recovery, ICP-MS, (percent) NIST 1547 plant NIST 2709 soil NIST 2583 dust NIST 2582 paint Ultrasonic Bath 104 ±5 93 ±1 108 ±11 96 ±3 15.0 Pollution Prevention 15.1 Pollution prevention encompasses any technique that reduces or eliminates the quantity and/or toxicity of waste at the point of generation. Numerous opportunities for pollution prevention exist in laboratory operations. Whenever feasible, laboratory personnel should use pollution prevention techniques to address their waste generation. The sources of pollution generated with this procedure are waste acid extracts and Pb-containing solutions. 15.2 For information about pollution prevention that may be applicable to laboratories and research institutions, consult Less is Better: Laboratory Chemical Management for Waste Reduction, available from the American Chemical Society's Department of Government Relations and Science Policy, 1155 16th St. NW., Washington, DC 20036, www.acs.org. 16.0 Waste Management 16.1 Laboratory waste management practices must be conducted consistent with all applicable rules and regulations. Laboratories are urged to protect air, water, and land by minimizing all releases from hood and bench operations, complying with the letter and spirit of any sewer and discharge permits and regulations, and by complying with all solid and hazardous waste regulation. For further information on waste management, consult The Waste Management Manual for Laboratory Personnel available from the American Chemical Society listed in Section 15.2 of this method. 16.2 Waste HNO 3 17.0 References FACDQ (2007). Report of the Federal Advisory Committee on Detection and Quantitation Approaches and Uses in Clean Water Act Programs, submitted to the U.S. EPA December 2007. Available: http://water.epa.gov/scitech/methods/cwa/det/upload/final-report-200712.pdf. Rice J (2013). Results from the Development of a New Federal Reference Method (FRM) for Lead in Total Suspended Particulate (TSP) Matter. Docket # EPA-HQ-OAR-2012-0210. U.S. EPA (2007). Method 6020A—Inductively Coupled Plasma Mass Spectrometry. U.S. Environmental Protection Agency. Revision 1, February 2007. Available: http://www.epa.gov/osw/hazard/testmethods/sw846/pdfs/6020a.pdf. U.S. EPA (2011). A Laboratory Study of Procedures Evaluated by the Federal Advisory Committee on Detection and Quantitation Approaches and Uses in Clean Water Act Programs. December 2011. Available: http://water.epa.gov/scitech/methods/cwa/det/upload/fac_report_2009.pdf. [78 FR 40004, July 3, 2013] Appendix H to Part 50—Interpretation of the 1-Hour Primary and Secondary National Ambient Air Quality Standards for Ozone 1. General This appendix explains how to determine when the expected number of days per calendar year with maximum hourly average concentrations above 0.12 ppm (235 µg/m 3 The basic principle in making this determination is relatively straightforward. Most of the complications that arise in determining the expected number of annual exceedances relate to accounting for incomplete sampling. In general, the average number of exceedances per calendar year must be less than or equal to 1. In its simplest form, the number of exceedances at a monitoring site would be recorded for each calendar year and then averaged over the past 3 calendar years to determine if this average is less than or equal to 1. 2. Interpretation of Expected Exceedances The ozone standard states that the expected number of exceedances per year must be less than or equal to 1. The statistical term “expected number” is basically an arithmetic average. The following example explains what it would mean for an area to be in compliance with this type of standard. Suppose a monitoring station records a valid daily maximum hourly average ozone value for every day of the year during the past 3 years. At the end of each year, the number of days with maximum hourly concentrations above 0.12 ppm is determined and this number is averaged with the results of previous years. As long as this average remains “less than or equal to 1,” the area is in compliance. 3. Estimating the Number of Exceedances for a Year In general, a valid daily maximum hourly average value may not be available for each day of the year, and it will be necessary to account for these missing values when estimating the number of exceedances for a particular calendar year. The purpose of these computations is to determine if the expected number of exceedances per year is less than or equal to 1. Thus, if a site has two or more observed exceedances each year, the standard is not met and it is not necessary to use the procedures of this section to account for incomplete sampling. The term “missing value” is used here in the general sense to describe all days that do not have an associated ozone measurement. In some cases, a measurement might actually have been missed but in other cases no measurement may have been scheduled for that day. A daily maximum ozone value is defined to be the highest hourly ozone value recorded for the day. This daily maximum value is considered to be valid if 75 percent of the hours from 9:01 a.m. to 9:00 p.m. (LST) were measured or if the highest hour is greater than the level of the standard. In some areas, the seasonal pattern of ozone is so pronounced that entire months need not be sampled because it is extremely unlikely that the standard would be exceeded. Any such waiver of the ozone monitoring requirement would be handled under provisions of 40 CFR, part 58. Some allowance should also be made for days for which valid daily maximum hourly values were not obtained but which would quite likely have been below the standard. Such an allowance introduces a complication in that it becomes necessary to define under what conditions a missing value may be assumed to have been less than the level of the standard. The following criterion may be used for ozone: A missing daily maximum ozone value may be assumed to be less than the level of the standard if the valid daily maxima on both the preceding day and the following day do not exceed 75 percent of the level of the standard. Let z denote the number of missing daily maximum values that may be assumed to be less than the standard. Then the following formula shall be used to estimate the expected number of exceedances for the year: (*Indicates multiplication.) where: e = the estimated number of exceedances for the year, N = the number of required monitoring days in the year, n = the number of valid daily maxima, v = the number of daily values above the level of the standard, and z = the number of days assumed to be less than the standard level. This estimated number of exceedances shall be rounded to one decimal place (fractional parts equal to 0.05 round up). It should be noted that N will be the total number of days in the year unless the appropriate Regional Administrator has granted a waiver under the provisions of 40 CFR part 58. The above equation may be interpreted intuitively in the following manner. The estimated number of exceedances is equal to the observed number of exceedances (v) plus an increment that accounts for incomplete sampling. There were (N-n) missing values for the year but a certain number of these, namely z, were assumed to be less than the standard. Therefore, (N-n-z) missing values are considered to include possible exceedances. The fraction of measured values that are above the level of the standard is v/n. It is assumed that this same fraction applies to the (N-n-z) missing values and that (v/n)*(N-n-z) of these values would also have exceeded the level of the standard. [44 FR 8220, Feb. 8, 1979, as amended at 62 FR 38895, July 18, 1997] Appendix I to Part 50—Interpretation of the 8-Hour Primary and Secondary National Ambient Air Quality Standards for Ozone 1. General. This appendix explains the data handling conventions and computations necessary for determining whether the national 8-hour primary and secondary ambient air quality standards for ozone specified in § 50.10 are met at an ambient ozone air quality monitoring site. Ozone is measured in the ambient air by a reference method based on appendix D of this part. Data reporting, data handling, and computation procedures to be used in making comparisons between reported ozone concentrations and the level of the ozone standard are specified in the following sections. Whether to exclude, retain, or make adjustments to the data affected by stratospheric ozone intrusion or other natural events is subject to the approval of the appropriate Regional Administrator. 2. Primary and Secondary Ambient Air Quality Standards for Ozone. 2.1 Data Reporting and Handling Conventions. 2.1.1 Computing 8-hour averages. 2.1.2 Daily maximum 8-hour average concentrations. (b) An ozone monitoring day shall be counted as a valid day if valid 8-hour averages are available for at least 75% of possible hours in the day ( i.e. 2.2 Primary and Secondary Standard-related Summary Statistic. 2.3 Comparisons with the Primary and Secondary Ozone Standards. (b) This comparison shall be based on three consecutive, complete calendar years of air quality monitoring data. This requirement is met for the three year period at a monitoring site if daily maximum 8-hour average concentrations are available for at least 90%, on average, of the days during the designated ozone monitoring season, with a minimum data completeness in any one year of at least 75% of the designated sampling days. When computing whether the minimum data completeness requirements have been met, meteorological or ambient data may be sufficient to demonstrate that meteorological conditions on missing days were not conducive to concentrations above the level of the standard. Missing days assumed less than the level of the standard are counted for the purpose of meeting the data completeness requirement, subject to the approval of the appropriate Regional Administrator. (c) Years with concentrations greater than the level of the standard shall not be ignored on the ground that they have less than complete data. Thus, in computing the 3-year average fourth maximum concentration, calendar years with less than 75% data completeness shall be included in the computation if the average annual fourth maximum 8-hour concentration is greater than the level of the standard. (d) Comparisons with the primary and secondary ozone standards are demonstrated by examples 1 and 2 in paragraphs (d)(1) and (d) (2) respectively as follows: (1) As shown in example 1, the primary and secondary standards are met at this monitoring site because the 3-year average of the annual fourth-highest daily maximum 8-hour average ozone concentrations ( i.e. Example 1. Ambient monitoring site attaining the primary and secondary ozone standards Year Percent Valid Days 1st Highest Daily Max 8-hour Conc. (ppm) 2nd Highest Daily Max 8-hour Conc. (ppm) 3rd Highest Daily Max 8-hour Conc. (ppm) 4th Highest Daily Max 8-hour Conc. (ppm) 5th Highest Daily Max 8-hour Conc. (ppm) 1993 100% 0.092 0.091 0.090 0.088 0.085 1994 96% 0.090 0.089 0.086 0.084 0.080 1995 98% 0.087 0.085 0.083 0.080 0.075 Average 98% (2) As shown in example 2, the primary and secondary standards are not met at this monitoring site because the 3-year average of the fourth-highest daily maximum 8-hour average ozone concentrations ( i.e. Example 2. Ambient Monitoring Site Failing to Meet the Primary and Secondary Ozone Standards Year Percent Valid Days 1st Highest Daily Max 8-hour Conc. (ppm) 2nd Highest Daily Max 8-hour Conc. (ppm) 3rd Highest Daily Max 8-hour Conc. (ppm) 4th Highest Daily Max 8-hour Conc. (ppm) 5th Highest Daily Max 8-hour Conc. (ppm) 1993 96% 0.105 0.103 0.103 0.102 0.102 1994 74% 0.090 0.085 0.082 0.080 0.078 1995 98% 0.103 0.101 0.101 0.097 0.095 Average 89% 3. Design Values for Primary and Secondary Ambient Air Quality Standards for Ozone. [62 FR 38895, July 18, 1997] Appendix J to Part 50—Reference Method for the Determination of Particulate Matter as PM 10 1.0 Applicability. 1.1 This method provides for the measurement of the mass concentration of particulate matter with an aerodynamic diameter less than or equal to a nominal 10 micrometers (PM 1O 10 2.0 Principle. 2.1 An air sampler draws ambient air at a constant flow rate into a specially shaped inlet where the suspended particulate matter is inertially separated into one or more size fractions within the PM 10 1O 2.2 Each filter is weighed (after moisture equilibration) before and after use to determine the net weight (mass) gain due to collected PM 10 10 10 3 10 10 2.3 A method based on this principle will be considered a reference method only if (a) the associated sampler meets the requirements specified in this appendix and the requirements in part 53 of this chapter, and (b) the method has been designated as a reference method in accordance with part 53 of this chapter. 3.0 Range. 3.1 The lower limit of the mass concentration range is determined by the repeatability of filter tare weights, assuming the nominal air sample volume for the sampler. For samplers having an automatic filter-changing mechanism, there may be no upper limit. For samplers that do not have an automatic filter-changing mechanism, the upper limit is determined by the filter mass loading beyond which the sampler no longer maintains the operating flow rate within specified limits due to increased pressure drop across the loaded filter. This upper limit cannot be specified precisely because it is a complex function of the ambient particle size distribution and type, humidity, filter type, and perhaps other factors. Nevertheless, all samplers should be capable of measuring 24-hour PM 10 3 4.0 Precision. 4.1 The precision of PM 10 3 10 3 10 3 10 10 5.0 Accuracy. 5.1 Because the size of the particles making up ambient particulate matter varies over a wide range and the concentration of particles varies with particle size, it is difficult to define the absolute accuracy of PM 10 10 10 10 6.0 Potential Sources of Error. 6.1 Volatile Particles. 3 6.2 Artifacts. 10 4 5 6 5 7 8 9 10 8 11 12 10 6.3 Humidity. 6.4 Filter Handling. 6.5 Flow Rate Variation. 6.6 Air Volume Determination. 7.0 Apparatus. 7.1 PM 10 Sampler. 7.1.1 The sampler shall be designed to: a. Draw the air sample into the sampler inlet and through the particle collection filter at a uniform face velocity. b. Hold and seal the filter in a horizontal position so that sample air is drawn downward through the filter. c. Allow the filter to be installed and removed conveniently. d. Protect the filter and sampler from precipitation and prevent insects and other debris from being sampled. e. Minimize air leaks that would cause error in the measurement of the air volume passing through the filter. f. Discharge exhaust air at a sufficient distance from the sampler inlet to minimize the sampling of exhaust air. g. Minimize the collection of dust from the supporting surface. 7.1.2 The sampler shall have a sample air inlet system that, when operated within a specified flow rate range, provides particle size discrimination characteristics meeting all of the applicable performance specifications prescribed in part 53 of this chapter. The sampler inlet shall show no significant wind direction dependence. The latter requirement can generally be satisfied by an inlet shape that is circularly symmetrical about a vertical axis. 7.1.3 The sampler shall have a flow control device capable of maintaining the sampler's operating flow rate within the flow rate limits specified for the sampler inlet over normal variations in line voltage and filter pressure drop. 7.1.4 The sampler shall provide a means to measure the total flow rate during the sampling period. A continuous flow recorder is recommended but not required. The flow measurement device shall be accurate to ±2 percent. 7.1.5 A timing/control device capable of starting and stopping the sampler shall be used to obtain a sample collection period of 24 ±1 hr (1,440 ±60 min). An elapsed time meter, accurate to within ±15 minutes, shall be used to measure sampling time. This meter is optional for samplers with continuous flow recorders if the sampling time measurement obtained by means of the recorder meets the ±15 minute accuracy specification. 7.1.6 The sampler shall have an associated operation or instruction manual as required by part 53 of this chapter which includes detailed instructions on the calibration, operation, and maintenance of the sampler. 7.2 Filters. 7.2.1 Filter Medium. 10 7.2.2 Collection Efficiency. 7.2.3 Integrity. 3 10 i.e. 7.2.4 Alkalinity. 7.3 Flow Rate Transfer Standard. 7.4 Filter Conditioning Environment. 7.4.1 Temperature range: 15 to 30 C. 7.4.2 Temperature control: ±3 C. 7.4.3 Humidity range: 20% to 45% RH. 7.4.4 Humidity control: ±5% RH. 7.5 Analytical Balance. 3 3 8.0 Calibration. 8.1 General Requirements. 8.1.1 Calibration of the sampler's flow measurement device is required to establish traceability of subsequent flow measurements to a primary standard. A flow rate transfer standard calibrated against a primary flow or volume standard shall be used to calibrate or verify the accuracy of the sampler's flow measurement device. 8.1.2 Particle size discrimination by inertial separation requires that specific air velocities be maintained in the sampler's air inlet system. Therefore, the flow rate through the sampler's inlet must be maintained throughout the sampling period within the design flow rate range specified by the manufacturer. Design flow rates are specified as actual volumetric flow rates, measured at existing conditions of temperature and pressure (Q a 10 std 8.2 Flow Rate Calibration Procedure. 8.2.1 PM 10 a std a 10 8.2.2 Calibrate the flow rate transfer standard against a primary flow or volume standard traceable to NBS. Establish a calibration relationship (e.g., an equation or family of curves) such that traceability to the primary standard is accurate to within 2 percent over the expected range of ambient conditions ( i.e. 8.2.3 Following the sampler manufacturer's instruction manual, remove the sampler inlet and connect the flow rate transfer standard to the sampler such that the transfer standard accurately measures the sampler's flow rate. Make sure there are no leaks between the transfer standard and the sampler. 8.2.4 Choose a minimum of three flow rates (actual m 3 3 8.2.5 Following calibration, verify that the sampler is operating at its design flow rate (actual m 3 8.2.6 Replace the sampler inlet. 9.0 Procedure. 9.1 The sampler shall be operated in accordance with the specific guidance provided in the sampler manufacturer's instruction manual and in Reference 2. The general procedure given here assumes that the sampler's flow rate calibration is based on flow rates at ambient conditions (Q a 10 9.2 Inspect each filter for pinholes, particles, and other imperfections. Establish a filter information record and assign an identification number to each filter. 9.3 Equilibrate each filter in the conditioning environment (see 7.4) for at least 24 hours. 9.4 Following equilibration, weigh each filter and record the presampling weight with the filter identification number. 9.5 Install a preweighed filter in the sampler following the instructions provided in the sampler manufacturer's instruction manual. 9.6 Turn on the sampler and allow it to establish run-temperature conditions. Record the flow indicator reading and, if needed, the ambient temperature and barometric pressure. Determine the sampler flow rate (actual m 3 9.7 If the flow rate is outside the acceptable range specified by the manufacturer, check for leaks, and if necessary, adjust the flow rate to the specified setpoint. Stop the sampler. 9.8 Set the timer to start and stop the sampler at appropriate times. Set the elapsed time meter to zero or record the initial meter reading. 9.9 Record the sample information (site location or identification number, sample date, filter identification number, and sampler model and serial number). 9.10 Sample for 24 ±1 hours. 9.11 Determine and record the average flow rate (Q a 3 9.12 Carefully remove the filter from the sampler, following the sampler manufacturer's instruction manual. Touch only the outer edges of the filter. 9.13 Place the filter in a protective holder or container (e.g., petri dish, glassine envelope, or manila folder). 9.14 Record any factors such as meteorological conditions, construction activity, fires or dust storms, etc., that might be pertinent to the measurement on the filter information record. 9.15 Transport the exposed sample filter to the filter conditioning environment as soon as possible for equilibration and subsequent weighing. 9.16 Equilibrate the exposed filter in the conditioning environment for at least 24 hours under the same temperature and humidity conditions used for presampling filter equilibration (see 9.3). 9.17 Immediately after equilibration, reweigh the filter and record the postsampling weight with the filter identification number. 10.0 Sampler Maintenance. 10.1 The PM 10 11.0 Calculations. 11.1 Calculate the average flow rate over the sampling period corrected to EPA reference conditions as Q std a std Q std a av av std std where Q std 3 Q a 3 P av T av T std P std 11.2 Calculate the total volume of air sampled as: V std std where V std 3 t = sampling time, min. 11.3 Calculate the PM 10 PM 10 f i 6 std where PM 10 10 3 W f i 1O 10 6 Note: If more than one size fraction in the PM 10 f i 10 12.0 References. 1. Quality Assurance Handbook for Air Pollution Measurement Systems, Volume I, Principles. EPA-600/9-76-005, March 1976. Available from CERI, ORD Publications, U.S. Environmental Protection Agency, 26 West St. Clair Street, Cincinnati, OH 45268. 2. Quality Assurance Handbook for Air Pollution Measurement Systems, Volume II, Ambient Air Specific Methods. EPA-600/4-77-027a, May 1977. Available from CERI, ORD Publications, U.S. Environmental Protection Agency, 26 West St. Clair Street, Cincinnati, OH 45268. 3. Clement, R.E., and F.W. Karasek. Sample Composition Changes in Sampling and Analysis of Organic Compounds in Aerosols. Int. J. Environ. Analyt. Chem., 7:109, 1979. 4. Lee, R.E., Jr., and J. Wagman. A Sampling Anomaly in the Determination of Atmospheric Sulfate Concentration. Amer. Ind. Hyg. Assoc. J., 27:266, 1966. 5. Appel, B.R., S.M. Wall, Y. Tokiwa, and M. Haik. Interference Effects in Sampling Particulate Nitrate in Ambient Air. Atmos. Environ., 13:319, 1979. 6. Coutant, R.W. Effect of Environmental Variables on Collection of Atmospheric Sulfate. Environ. Sci. Technol., 11:873, 1977. 7. Spicer, C.W., and P. Schumacher. Interference in Sampling Atmospheric Particulate Nitrate. Atmos. Environ., 11:873, 1977. 8. Appel, B.R., Y. Tokiwa, and M. Haik. Sampling of Nitrates in Ambient Air. Atmos. Environ., 15:283, 1981. 9. Spicer, C.W., and P.M. Schumacher. Particulate Nitrate: Laboratory and Field Studies of Major Sampling Interferences. Atmos. Environ., 13:543, 1979. 10. Appel, B.R. Letter to Larry Purdue, U.S. EPA, Environmental Monitoring and Support Laboratory. March 18, 1982, Docket No. A-82-37, II-I-1. 11. Pierson, W.R., W.W. Brachaczek, T.J. Korniski, T.J. Truex, and J.W. Butler. Artifact Formation of Sulfate, Nitrate, and Hydrogen Ion on Backup Filters: Allegheny Mountain Experiment. J. Air Pollut. Control Assoc., 30:30, 1980. 12. Dunwoody, C.L. Rapid Nitrate Loss From PM 10 13. Harrell, R.M. Measuring the Alkalinity of Hi-Vol Air Filters. EMSL/RTP-SOP-QAD-534, October 1985. Available from the U.S. Environmental Protection Agency, EMSL/QAD, Research Triangle Park, NC 27711. 14. Smith, F., P.S. Wohlschlegel, R.S.C. Rogers, and D.J. Mulligan. Investigation of Flow Rate Calibration Procedures Associated With the High Volume Method for Determination of Suspended Particulates. EPA-600/4-78-047, U.S. Environmental Protection Agency, Research Triangle Park, NC 27711, 1978. [52 FR 24664, July 1, 1987; 52 FR 29467, Aug. 7, 1987] Appendix K to Part 50—Interpretation of the National Ambient Air Quality Standards for Particulate Matter 1.0 General (a) This appendix explains the computations necessary for analyzing particulate matter data to determine attainment of the 24-hour standards specified in 40 CFR 50.6. For the primary and secondary standards, particulate matter is measured in the ambient air as PM 10 (b) The terms used in this appendix are defined as follows: Average Collocated monitors e.g., 10 Combined site data record Daily value for PM 10 10 Exceedance 3 i.e., Expected annual value Primary monitors Year (c) Although the discussion in this appendix focuses on monitored data, the same principles apply to modeling data, subject to EPA modeling guidelines. 2.0 Attainment Determinations 2.1 24-Hour Primary and Secondary Standards (a) Under 40 CFR 50.6(a) the 24-hour primary and secondary standards are attained when the expected number of exceedances per year at each monitoring site is less than or equal to one. In the simplest case, the number of expected exceedances at a site is determined by recording the number of exceedances in each calendar year and then averaging them over the past 3 calendar years. Situations in which 3 years of data are not available and possible adjustments for unusual events or trends are discussed in sections 2.3 and 2.4 of this appendix. Further, when data for a year are incomplete, it is necessary to compute an estimated number of exceedances for that year by adjusting the observed number of exceedances. This procedure, performed by calendar quarter, is described in section 3.0 of this appendix. The expected number of exceedances is then estimated by averaging the individual annual estimates for the past 3 years. (b) The comparison with the allowable expected exceedance rate of one per year is made in terms of a number rounded to the nearest tenth (fractional values equal to or greater than 0.05 are to be rounded up; e.g., an exceedance rate of 1.05 would be rounded to 1.1, which is the lowest rate for nonattainment). 2.2 Reserved 2.3 Data Requirements (a) 40 CFR 58.12 specifies the required minimum frequency of sampling for PM 10 10 (b) To demonstrate attainment of the 24-hour standards at a monitoring site, the monitor must provide sufficient data to perform the required calculations of sections 3.0 and 4.0 of this appendix. The amount of data required varies with the sampling frequency, data capture rate and the number of years of record. In all cases, 3 years of representative monitoring data that meet the 75 percent criterion of the previous paragraph should be utilized, if available, and would suffice. More than 3 years may be considered, if all additional representative years of data meeting the 75 percent criterion are utilized. Data not meeting these criteria may also suffice to show attainment; however, such exceptions will have to be approved by the appropriate Regional Administrator in accordance with EPA guidance. (c) There are less stringent data requirements for showing that a monitor has failed an attainment test and thus has recorded a violation of the particulate matter standards. Although it is generally necessary to meet the minimum 75 percent data capture requirement per quarter to use the computational equations described in section 3.0 of this appendix, this criterion does not apply when less data is sufficient to unambiguously establish nonattainment. The following examples illustrate how nonattainment can be demonstrated when a site fails to meet the completeness criteria. Nonattainment of the 24-hour primary standards can be established by the observed annual number of exceedances (e.g., four observed exceedances in a single year), or by the estimated number of exceedances derived from the observed number of exceedances and the required number of scheduled samples (e.g., two observed exceedances with every other day sampling). In both cases, expected annual values must exceed the levels allowed by the standards. (d) 24-hour average concentrations will be computed from submitted hourly PM 10 i.e., i.e., i.e., e.g., 3 2.4 Adjustment for Exceptional Events and Trends (a) An exceptional event is an uncontrollable event caused by natural sources of particulate matter or an event that is not expected to recur at a given location. Inclusion of such a value in the computation of exceedances or averages could result in inappropriate estimates of their respective expected annual values. To reduce the effect of unusual events, more than 3 years of representative data may be used. Alternatively, other techniques, such as the use of statistical models or the use of historical data could be considered so that the event may be discounted or weighted according to the likelihood that it will recur. The use of such techniques is subject to the approval of the appropriate Regional Administrator in accordance with EPA guidance. (b) In cases where long-term trends in emissions and air quality are evident, mathematical techniques should be applied to account for the trends to ensure that the expected annual values are not inappropriately biased by unrepresentative data. In the simplest case, if 3 years of data are available under stable emission conditions, this data should be used. In the event of a trend or shift in emission patterns, either the most recent representative year(s) could be used or statistical techniques or models could be used in conjunction with previous years of data to adjust for trends. The use of less than 3 years of data, and any adjustments are subject to the approval of the appropriate Regional Administrator in accordance with EPA guidance. 3.0 Computational Equations for the 24-Hour Standards (a) All computations shown in this appendix shall be implemented on a site-level basis. Site level concentration data shall be processed as follows: (1) The default dataset for PM 10 (2) If a daily value is not produced by the primary monitor for a particular day, but a value is available from a single collocated monitor, then that collocated monitor value shall be considered part of the combined site data record. If daily value data is available from two or more collocated monitors, the average of those collocated values shall be used as the daily value. The data record resulting from this procedure is referred to as the “combined site data record.” (b) In certain circumstances, including but not limited to site closures or relocations, data from two nearby sites may be combined into a single site data record for the purpose of calculating a valid design value. The appropriate Regional Administrator may approve such combinations if the Regional Administrator determines that the measured concentrations do not differ substantially between the two sites, taking into consideration factors such as distance between sites, spatial and temporal patterns in air quality, local emissions and meteorology, jurisdictional boundaries, and terrain features. 3.1 Estimating Exceedances for a Year (a) If PM 10 10 Where: e q v q N q n q 10 q = the index for calendar quarter, q = 1, 2, 3 or 4. (b) The estimated number of exceedances for a calendar quarter must be rounded to the nearest hundredth (fractional values equal to or greater than 0.005 must be rounded up). (c) The estimated number of exceedances for the year, e, is the sum of the estimates for each calendar quarter. (d) The estimated number of exceedances for a single year must be rounded to one decimal place (fractional values equal to or greater than 0.05 are to be rounded up). The expected number of exceedances is then estimated by averaging the individual annual estimates for the most recent 3 or more representative years of data. The expected number of exceedances must be rounded to one decimal place (fractional values equal to or greater than 0.05 are to be rounded up). (e) The adjustment for incomplete data will not be necessary for monitoring or modeling data which constitutes a complete record, i.e., 365 days per year. (f) To reduce the potential for overestimating the number of expected exceedances, the correction for missing data will not be required for a calendar quarter in which the first observed exceedance has occurred if: (1) There was only one exceedance in the calendar quarter; (2) Everyday sampling is subsequently initiated and maintained for 4 calendar quarters in accordance with 40 CFR 58.12; and (3) Data capture of 75 percent is achieved during the required period of everyday sampling. In addition, if the first exceedance is observed in a calendar quarter in which the monitor is already sampling every day, no adjustment for missing data will be made to the first exceedance if a 75 percent data capture rate was achieved in the quarter in which it was observed. Example 1 a. During a particular calendar quarter, 39 out of a possible 92 samples were recorded, with one observed exceedance of the 24-hour standard. Using Equation 1, the estimated number of exceedances for the quarter is: e q b. If the estimated exceedances for the other 3 calendar quarters in the year were 2.30, 0.0 and 0.0, then, using Equation 2, the estimated number of exceedances for the year is 2.36 + 2.30 + 0.0 + 0.0 which equals 4.66 or 4.7. If no exceedances were observed for the 2 previous years, then the expected number of exceedances is estimated by: ( 1/3 Example 2 In this example, everyday sampling was initiated following the first observed exceedance as required by 40 CFR 58.12. Accordingly, the first observed exceedance would not be adjusted for incomplete sampling. During the next three quarters, 1.2 exceedances were estimated. In this case, the estimated exceedances for the year would be 1.0 + 1.2 + 0.0 + 0.0 which equals 2.2. If, as before, no exceedances were observed for the two previous years, then the estimated exceedances for the 3-year period would then be ( 1/3 3.2 Adjustments for Non-Scheduled Sampling Days (a) If a systematic sampling schedule is used and sampling is performed on days in addition to the days specified by the systematic sampling schedule, e.g., during episodes of high pollution, then an adjustment must be made in the equation for the estimation of exceedances. Such an adjustment is needed to eliminate the bias in the estimate of the quarterly and annual number of exceedances that would occur if the chance of an exceedance is different for scheduled than for non-scheduled days, as would be the case with episode sampling. (b) The required adjustment treats the systematic sampling schedule as a stratified sampling plan. If the period from one scheduled sample until the day preceding the next scheduled sample is defined as a sampling stratum, then there is one stratum for each scheduled sampling day. An average number of observed exceedances is computed for each of these sampling strata. With nonscheduled sampling days, the estimated number of exceedances is defined as: Where: e q N q m q v j k j (c) Note that if only one sample value is recorded in each stratum, then Equation 3 reduces to Equation 1. Example 3 A monitoring site samples according to a systematic sampling schedule of one sample every 6 days, for a total of 15 scheduled samples in a quarter out of a total of 92 possible samples. During one 6-day period, potential episode levels of PM 10 Eq = (92/14) × (2/6 + 0 + . . . + 0) = 2.19. [71 FR 61224, Oct. 17, 2006, as amended at 89 FR 16380, Mar. 6, 2024] Appendix L to Part 50—Reference Method for the Determination of Fine Particulate Matter as PM 2.5 1.0 Applicability. 1.1 This method provides for the measurement of the mass concentration of fine particulate matter having an aerodynamic diameter less than or equal to a nominal 2.5 micrometers (PM 2.5 2.5 1.2 This method will be considered a reference method for purposes of part 58 of this chapter only if: (a) The associated sampler meets the requirements specified in this appendix and the applicable requirements in part 53 of this chapter, and (b) The method and associated sampler have been designated as a reference method in accordance with part 53 of this chapter. 1.3 PM 2.5 2.5 2.0 Principle. 2.1 An electrically powered air sampler draws ambient air at a constant volumetric flow rate into a specially shaped inlet and through an inertial particle size separator (impactor) where the suspended particulate matter in the PM 2.5 2.2 Each filter is weighed (after moisture and temperature conditioning) before and after sample collection to determine the net gain due to collected PM 2.5 2.5 2.5 3 3.0 PM 2.5 Measurement Range. 3.1 Lower concentration limit. 3 3 3.2 Upper concentration limit. 2.5 3 3.3 Sample period. 2.5 2.5 2.5 4.0 Accuracy. 4.1 Because the size and volatility of the particles making up ambient particulate matter vary over a wide range and the mass concentration of particles varies with particle size, it is difficult to define the accuracy of PM 2.5 2.5 2.5 2.5 4.2 Measurement system bias. 4.3 Audits with reference method samplers to determine system accuracy and bias. 2.5 4.4 Flow rate accuracy and bias. 2.5 5.0 Precision. 2.5 5.1 Tests to establish initial operational precision for each reference method sampler are specified as a part of the requirements for designation as a reference method under § 53.58 of this chapter. 5.2 Measurement System Precision. 6.0 Filter for PM 2.5 Sample Collection. 2.5 6.1 Size. 6.2 Medium. 6.3 Support ring. 6.4 Pore size. 6.5 Filter thickness. 6.6 Maximum pressure drop (clean filter). 2 6.7 Maximum moisture pickup. 6.8 Collection efficiency. 6.9 Filter weight stability. 6.9.1 Test for loose, surface particle contamination. 6.9.2 Test for temperature stability. 6.10 Alkalinity. 6.11 Supplemental requirements. 2.5 2.5 7.0 PM 2.5 Sampler. 7.1 Configuration. (a) Provide automatic control of sample volumetric flow rate and other operational parameters. (b) Monitor these operational parameters as well as ambient temperature and pressure. (c) Provide this information to the sampler operator at the end of each sample period in digital form, as specified in table L-1 of section 7.4.19 of this appendix. 7.2 Nature of specifications. 2.5 7.3 Design specifications. 7.3.1 Sample inlet assembly. 7.3.2 Inlet. 7.3.3 Downtube. 7.3.4 Particle size separator. TM 2.5 7.3.4.1 The impactor (particle size separator) shall be fabricated as indicated in Figures L-20 through L-24 of this appendix and shall meet all associated requirements. Following the manufacture and finishing of each upper impactor housing (Figure L-21 of this appendix), the dimension of the impaction jet must be verified by the manufacturer using Class ZZ go/no-go plug gauges that are traceable to NIST. 7.3.4.2 Impactor filter specifications: (a) Size. Circular, 35 to 37 mm diameter. (b) Medium. Borosilicate glass fiber, without binder. (c) Pore size. 1 to 1.5 micrometer, as measured by ASTM F 316-80. (d) Thickness. 300 to 500 micrometers. 7.3.4.3 Impactor oil specifications: (a) Composition. Dioctyl sebacate (DOS), single-compound diffusion oil. 7.3.4.5 A second cyclone-type separator is identified as a Tisch TE-PM 2.5 (b) Vapor pressure. Maximum 2 × 10 −8 (c) Viscosity. 36 to 40 centistokes at 25 °C. (d) Density. 1.06 to 1.07 g/cm 3 (e) Quantity. 1 mL ±0.1 mL. 7.3.4.4 The cyclone-type separator is identified as a BGI VSCC TM 7.3.5 Filter holder assembly. (a) The lower portion of the filter holder assembly shall be of a design and construction that: (1) Mates with the upper portion of the assembly to complete the filter holder assembly, (2) Completes both the external air seal and the internal filter cassette seal such that all seals are reliable over repeated filter changings, and (3) Facilitates repeated changing of the filter cassette by the sampler operator. (b) Leak-test performance requirements for the filter holder assembly are included in section 7.4.6 of this appendix. (c) If additional or multiple filters are stored in the sampler as part of an automatic sequential sample capability, all such filters, unless they are currently and directly installed in a sampling channel or sampling configuration (either active or inactive), shall be covered or (preferably) sealed in such a way as to: (1) Preclude significant exposure of the filter to possible contamination or accumulation of dust, insects, or other material that may be present in the ambient air, sampler, or sampler ventilation air during storage periods either before or after sampling; and (2) To minimize loss of volatile or semi-volatile PM sample components during storage of the filter following the sample period. 7.3.6 Flow rate measurement adapter. 7.3.7 Surface finish. 2 2 7.3.8 Sampling height. 7.4 Performance specifications. 7.4.1 Sample flow rate. 3 7.4.2 Sample air flow rate control system. 7.4.3 Sample flow rate regulation. 7.4.3.1 The volumetric flow rate, measured or averaged over intervals of not more than 5 minutes over a 24-hour period, shall not vary more than ±5 percent from the specified 16.67 L/min flow rate over the entire sample period. 7.4.3.2 The coefficient of variation (sample standard deviation divided by the mean) of the flow rate, measured over a 24-hour period, shall not be greater than 2 percent. 7.4.3.3 The amplitude of short-term flow rate pulsations, such as may originate from some types of vacuum pumps, shall be attenuated such that they do not cause significant flow measurement error or affect the collection of particles on the particle collection filter. 7.4.4 Flow rate cut off. 7.4.5 Flow rate measurement. 7.4.5.1 The sampler shall provide a means to measure and indicate the instantaneous sample air flow rate, which shall be measured as volumetric flow rate at the temperature and pressure of the sample air entering the inlet, with an accuracy of ±2 percent. The measured flow rate shall be available for display to the sampler operator at any time in either sampling or standby modes, and the measurement shall be updated at least every 30 seconds. The sampler shall also provide a simple means by which the sampler operator can manually start the sample flow temporarily during non-sampling modes of operation, for the purpose of checking the sample flow rate or the flow rate measurement system. 7.4.5.2 During each sample period, the sampler's flow rate measurement system shall automatically monitor the sample volumetric flow rate, obtaining flow rate measurements at intervals of not greater than 30 seconds. (a) Using these interval flow rate measurements, the sampler shall determine or calculate the following flow-related parameters, scaled in the specified engineering units: (1) The instantaneous or interval-average flow rate, in L/min. (2) The value of the average sample flow rate for the sample period, in L/min. (3) The value of the coefficient of variation (sample standard deviation divided by the average) of the sample flow rate for the sample period, in percent. (4) The occurrence of any time interval during the sample period in which the measured sample flow rate exceeds a range of ±5 percent of the average flow rate for the sample period for more than 5 minutes, in which case a warning flag indicator shall be set. (5) The value of the integrated total sample volume for the sample period, in m 3 (b) Determination or calculation of these values shall properly exclude periods when the sampler is inoperative due to temporary interruption of electrical power, under section 7.4.13 of this appendix, or flow rate cut off, under section 7.4.4 of this appendix. (c) These parameters shall be accessible to the sampler operator as specified in table L-1 of section 7.4.19 of this appendix. In addition, it is strongly encouraged that the flow rate for each 5-minute interval during the sample period be available to the operator following the end of the sample period. 7.4.6 Leak test capability. 7.4.6.1 External leakage. (a) The suggested technique for the operator to use for this leak test is as follows: (1) Remove the sampler inlet and installs the flow rate measurement adapter supplied with the sampler, under section 7.3.6 of this appendix. (2) Close the valve on the flow rate measurement adapter and use the sampler air pump to draw a partial vacuum in the sampler, including (at least) the impactor, filter holder assembly (filter in place), flow measurement device, and interconnections between these devices, of at least 55 mm Hg (75 cm water column), measured at a location downstream of the filter holder assembly. (3) Plug the flow system downstream of these components to isolate the components under vacuum from the pump, such as with a built-in valve. (4) Stop the pump. (5) Measure the trapped vacuum in the sampler with a built-in pressure measuring device. (6) (i) Measure the vacuum in the sampler with the built-in pressure measuring device again at a later time at least 10 minutes after the first pressure measurement. (ii) Caution: (7) Upon completion of the test, open the adaptor valve, remove the adaptor and plugs, and restore the sampler to the normal operating configuration. (b) The associated leak test procedure shall require that for successful passage of this test, the difference between the two pressure measurements shall not be greater than the number of mm of Hg specified for the sampler by the manufacturer, based on the actual internal volume of the sampler, that indicates a leak of less than 80 mL/min. (c) Variations of the suggested technique or an alternative external leak test technique may be required for samplers whose design or configuration would make the suggested technique impossible or impractical. The specific proposed external leak test procedure, or particularly an alternative leak test technique, proposed for a particular candidate sampler may be described and submitted to the EPA for specific individual acceptability either as part of a reference or equivalent method application under part 53 of this chapter or in writing in advance of such an intended application under part 53 of this chapter. 7.4.6.2 Internal, filter bypass leakage. (a) The suggested technique for the operator to use for this leak test is as follows: (1) Carry out an external leak test as provided under section 7.4.6.1 of this appendix which indicates successful passage of the prescribed external leak test. (2) Install a flow-impervious membrane material in the filter cassette, either with or without a filter, as appropriate, which effectively prevents air flow through the filter. (3) Use the sampler air pump to draw a partial vacuum in the sampler, downstream of the filter holder assembly, of at least 55 mm Hg (75 cm water column). (4) Plug the flow system downstream of the filter holder to isolate the components under vacuum from the pump, such as with a built-in valve. (5) Stop the pump. (6) Measure the trapped vacuum in the sampler with a built-in pressure measuring device. (7) Measure the vacuum in the sampler with the built-in pressure measuring device again at a later time at least 10 minutes after the first pressure measurement. (8) Remove the flow plug and membrane and restore the sampler to the normal operating configuration. (b) The associated leak test procedure shall require that for successful passage of this test, the difference between the two pressure measurements shall not be greater than the number of mm of Hg specified for the sampler by the manufacturer, based on the actual internal volume of the portion of the sampler under vacuum, that indicates a leak of less than 80 mL/min. (c) Variations of the suggested technique or an alternative internal, filter bypass leak test technique may be required for samplers whose design or configuration would make the suggested technique impossible or impractical. The specific proposed internal leak test procedure, or particularly an alternative internal leak test technique proposed for a particular candidate sampler may be described and submitted to the EPA for specific individual acceptability either as part of a reference or equivalent method application under part 53 of this chapter or in writing in advance of such intended application under part 53 of this chapter. 7.4.7 Range of operational conditions. 7.4.7.1 Ambient temperature. 7.4.7.2 Ambient relative humidity. 7.4.7.3 Barometric pressure range. 7.4.8 Ambient temperature sensor. 7.4.8.1 The ambient temperature sensor shall be mounted external to the sampler enclosure and shall have a passive, naturally ventilated sun shield. The sensor shall be located such that the entire sun shield is at least 5 cm above the horizontal plane of the sampler case or enclosure (disregarding the inlet and downtube) and external to the vertical plane of the nearest side or protuberance of the sampler case or enclosure. The maximum temperature measurement error of the ambient temperature measurement system shall be less than 1.6 °C at 1 m/s wind speed and 1000 W/m2 solar radiation intensity. 7.4.8.2 The ambient temperature sensor shall be of such a design and mounted in such a way as to facilitate its convenient dismounting and immersion in a liquid for calibration and comparison to the filter temperature sensor, under section 7.4.11 of this appendix. 7.4.8.3 This ambient temperature measurement shall be updated at least every 30 seconds during both sampling and standby (non-sampling) modes of operation. A visual indication of the current (most recent) value of the ambient temperature measurement, updated at least every 30 seconds, shall be available to the sampler operator during both sampling and standby (non-sampling) modes of operation, as specified in table L-1 of section 7.4.19 of this appendix. 7.4.8.4 This ambient temperature measurement shall be used for the purpose of monitoring filter temperature deviation from ambient temperature, as required by section 7.4.11 of this appendix, and may be used for purposes of effecting filter temperature control, under section 7.4.10 of this appendix, or computation of volumetric flow rate, under sections 7.4.1 to 7.4.5 of this appendix, if appropriate. 7.4.8.5 Following the end of each sample period, the sampler shall report the maximum, minimum, and average temperature for the sample period, as specified in table L-1 of section 7.4.19 of this appendix. 7.4.9 Ambient barometric sensor. 7.4.10 Filter temperature control (sampling and post-sampling). 7.4.11 Filter temperature sensor(s). 7.4.11.1 The sampler shall have the capability to monitor the temperature of the sample filter (all sample filters for sequential samplers) over the range of −30 to = 45 °C during both sampling and non-sampling periods. While the exact location of this temperature sensor is not explicitly specified, the filter temperature measurement system must demonstrate agreement, within 1 °C, with a test temperature sensor located within 1 cm of the center of the filter downstream of the filter during both sampling and non-sampling modes, as specified in the filter temperature measurement test described in part 53, subpart E of this chapter. This filter temperature measurement shall have a resolution of 0.1 °C and accuracy of ±1.0 °C, referenced as described in reference 3 in section 13.0 of this appendix. This temperature sensor shall be of such a design and mounted in such a way as to facilitate its reasonably convenient dismounting and immersion in a liquid for calibration and comparison to the ambient temperature sensor under section 7.4.8 of this appendix. 7.4.11.2 The filter temperature measurement shall be updated at least every 30 seconds during both sampling and standby (non-sampling) modes of operation. A visual indication of the current (most recent) value of the filter temperature measurement, updated at least every 30 seconds, shall be available to the sampler operator during both sampling and standby (non-sampling) modes of operation, as specified in table L-1 of section 7.4.19 of this appendix. 7.4.11.3 For sequential samplers, the temperature of each filter shall be measured individually unless it can be shown, as specified in the filter temperature measurement test described in § 53.57 of this chapter, that the temperature of each filter can be represented by fewer temperature sensors. 7.4.11.4 The sampler shall also provide a warning flag indicator following any occurrence in which the filter temperature (any filter temperature for sequential samplers) exceeds the ambient temperature by more than 5 °C for more than 30 consecutive minutes during either the sampling or post-sampling periods of operation, as specified in table L-1 of section 7.4.19 of this appendix, under section 10.12 of this appendix, regarding sample validity when a warning flag occurs. It is further recommended (not required) that the sampler be capable of recording the maximum differential between the measured filter temperature and the ambient temperature and its time and date of occurrence during both sampling and post-sampling (non-sampling) modes of operation and providing for those data to be accessible to the sampler operator following the end of the sample period, as suggested in table L-1 of section 7.4.19 of this appendix. 7.4.12 Clock/timer system. (a) The sampler shall have a programmable real-time clock timing/control system that: (1) Is capable of maintaining local time and date, including year, month, day-of-month, hour, minute, and second to an accuracy of ±1.0 minute per month. (2) Provides a visual indication of the current system time, including year, month, day-of-month, hour, and minute, updated at least each minute, for operator verification. (3) Provides appropriate operator controls for setting the correct local time and date. (4) Is capable of starting the sample collection period and sample air flow at a specific, operator-settable time and date, and stopping the sample air flow and terminating the sampler collection period 24 hours (1440 minutes) later, or at a specific, operator-settable time and date. (b) These start and stop times shall be readily settable by the sampler operator to within ±1.0 minute. The system shall provide a visual indication of the current start and stop time settings, readable to ±1.0 minute, for verification by the operator, and the start and stop times shall also be available via the data output port, as specified in table L-1 of section 7.4.19 of this appendix. Upon execution of a programmed sample period start, the sampler shall automatically reset all sample period information and warning flag indications pertaining to a previous sample period. Refer also to section 7.4.15.4 of this appendix regarding retention of current date and time and programmed start and stop times during a temporary electrical power interruption. 7.4.13 Sample time determination. 2.5 7.4.14 Outdoor environmental enclosure. 7.4.15 Electrical power supply. 7.4.15.1 The sampler shall be operable and function as specified herein when operated on an electrical power supply voltage of 105 to 125 volts AC (RMS) at a frequency of 59 to 61 Hz. Optional operation as specified at additional power supply voltages and/or frequencies shall not be precluded by this requirement. 7.4.15.2 The design and construction of the sampler shall comply with all applicable National Electrical Code and Underwriters Laboratories electrical safety requirements. 7.4.15.3 The design of all electrical and electronic controls shall be such as to provide reasonable resistance to interference or malfunction from ordinary or typical levels of stray electromagnetic fields (EMF) as may be found at various monitoring sites and from typical levels of electrical transients or electronic noise as may often or occasionally be present on various electrical power lines. 7.4.15.4 In the event of temporary loss of electrical supply power to the sampler, the sampler shall not be required to sample or provide other specified functions during such loss of power, except that the internal clock/timer system shall maintain its local time and date setting within ±1 minute per week, and the sampler shall retain all other time and programmable settings and all data required to be available to the sampler operator following each sample period for at least 7 days without electrical supply power. When electrical power is absent at the operator-set time for starting a sample period or is interrupted during a sample period, the sampler shall automatically start or resume sampling when electrical power is restored, if such restoration of power occurs before the operator-set stop time for the sample period. 7.4.15.5 The sampler shall have the capability to record and retain a record of the year, month, day-of-month, hour, and minute of the start of each power interruption of more than 1 minute duration, up to 10 such power interruptions per sample period. (More than 10 such power interruptions shall invalidate the sample, except where an exceedance is measured, under section 3.3 of this appendix.) The sampler shall provide for these power interruption data to be available to the sampler operator following the end of the sample period, as specified in table L-1 of section 7.4.19 of this appendix. 7.4.16 Control devices and operator interface. 7.4.17 Data output port requirement. 7.4.18 Operation/instruction manual. 7.4.19 Data reporting requirements. Table L-1 to Appendix L of Part 50—Summary of Information To Be Provided by the Sampler Information to be provided Appendix L section Availability Format Anytime 1 End of 2 Visual 3 Data 4 Digital 5 Units Flow rate, 30-second maximum interval 7.4.5.1 ✓ ✓ * XX.X L/min Flow rate, average for the sample period 7.4.5.2 * ✓ * ✓ XX.X L/min Flow rate, CV, for sample period 7.4.5.2 * ✓ * ✓ XX.X % Flow rate, 5-min. average out of spec. (FLAG 6 7.4.5.2 ✓ ✓ ✓ ✓▪ On/Off Sample volume, total 7.4.5.2 * ✓ ✓ ✓ XX.X m 3 Temperature, ambient, 30-second interval 7.4.8 ✓ ✓ XX.X °C Temperature, ambient, min., max., average for the sample period 7.4.8 * ✓ ✓ ✓▪ XX.X °C Baro. pressure, ambient, 30-second interval 7.4.9 ✓ ✓ XXX mm Hg Baro. pressure, ambient, min., max., average for the sample period 7.4.9 * ✓ ✓ ✓▪ XXX mm Hg Filter temperature, 30-second interval 7.4.11 ✓ ✓ XX.X °C Filter temp. differential, 30-second interval, out of spec. (FLAG 6 7.4.11 * ✓ ✓ ✓▪ On/Off Filter temp., maximum differential from ambient, date, time of occurrence 7.4.11 * * * * X.X, YY/MM/DD HH.mm °C, Yr/Mon/Day Hrs. min Date and Time 7.4.12 ✓ ✓ YY/MM/DD HH.mm Yr/Mon/Day Hrs. min Sample start and stop time settings 7.4.12 ✓ ✓ ✓ ✓ YY/MM/DD HH.mm Yr/Mon/Day Hrs. min Sample period start time 7.4.12 ✓ ✓ ✓ YY/MM/DD HH.mm Yr/Mon/Day Hrs. min Elapsed sample time 7.4.13 * ✓ ✓ ✓ HH.mm Hrs. min Elapsed sample time, out of spec. (FLAG 6 7.4.13 ✓ ✓ ✓▪ On/Off Power interruptions ≤1 min., start time of first 10 7.4.15.5 * ✓ * ✓ 1HH.mm, 2HH.mm, etc. Hrs. min User-entered information, such as sampler and site identification 7.4.16 ✓ ✓ ✓ ✓▪ As entered ✓ Provision of this information is required. * Provision of this information is optional. If information related to the entire sample period is optionally provided prior to the end of the sample period, the value provided should be the value calculated for the portion of the sampler period completed up to the time the information is provided. ▪ Indicates that this information is also required to be provided to the Air Quality System (AQS) data bank; see § 58.16 of this chapter. For ambient temperature and barometric pressure, only the average for the sample period must be reported. 1. Information is required to be available to the operator at any time the sampler is operating, whether sampling or not. 2. Information relates to the entire sampler period and must be provided following the end of the sample period until reset manually by the operator or automatically by the sampler upon the start of a new sample period. 3. Information shall be available to the operator visually. 4. Information is to be available as digital data at the sampler's data output port specified in section 7.4.16 of this appendix following the end of the sample period until reset manually by the operator or automatically by the sampler upon the start of a new sample period. 5. Digital readings, both visual and data output, shall have not less than the number of significant digits and resolution specified. 6. Flag warnings may be displayed to the operator by a single flag indicator or each flag may be displayed individually. Only a set (on) flag warning must be indicated; an off (unset) flag may be indicated by the absence of a flag warning. Sampler users should refer to section 10.12 of this appendix regarding the validity of samples for which the sampler provided an associated flag warning. 8.0 Filter Weighing. 8.1 Analytical balance. 8.2 Filter conditioning. 8.2.1 Mean temperature. 8.2.2 Temperature control. 8.2.3 Mean humidity. 8.2.4 Humidity control. 8.2.5 Conditioning time. 8.3 Weighing procedure. 8.3.1 New filters should be placed in the conditioning environment immediately upon arrival and stored there until the pre-sampling weighing. See reference 2 in section 13.0 of this appendix for additional guidance. 8.3.2 The analytical balance shall be located in the same controlled environment in which the filters are conditioned. The filters shall be weighed immediately following the conditioning period without intermediate or transient exposure to other conditions or environments. 8.3.3 Filters must be conditioned at the same conditions (humidity within ±5 relative humidity percent) before both the pre- and post-sampling weighings. 8.3.4 Both the pre- and post-sampling weighings should be carried out on the same analytical balance, using an effective technique to neutralize static charges on the filter, under reference 2 in section 13.0 of this appendix. If possible, both weighings should be carried out by the same analyst. 8.3.5 The pre-sampling (tare) weighing shall be within 30 days of the sampling period. 8.3.6 The post-sampling conditioning and weighing shall be completed within 240 hours (10 days) after the end of the sample period, unless the filter sample is maintained at temperatures below the average ambient temperature during sampling (or 4 °C or below for average sampling temperatures less than 4 °C) during the time between retrieval from the sampler and the start of the conditioning, in which case the period shall not exceed 30 days. Reference 2 in section 13.0 of this appendix has additional guidance on transport of cooled filters. 8.3.7 Filter blanks. 8.3.7.1 New field blank filters shall be weighed along with the pre-sampling (tare) weighing of each lot of PM 2.5 8.3.7.2 New laboratory blank filters shall be weighed along with the pre-sampling (tare) weighing of each set of PM 2.5 8.3.8 Additional guidance for proper filter weighing and related quality assurance activities is provided in reference 2 in section 13.0 of this appendix. 9.0 Calibration. 9.1 General requirements. 9.1.1 Multipoint calibration and single-point verification of the sampler's flow rate measurement device must be performed periodically to establish and maintain traceability of subsequent flow measurements to a flow rate standard. 9.1.2 An authoritative flow rate standard shall be used for calibrating or verifying the sampler's flow rate measurement device with an accuracy of ±2 percent. The flow rate standard shall be a separate, stand-alone device designed to connect to the flow rate measurement adapter, Figure L-30 of this appendix. This flow rate standard must have its own certification and be traceable to a National Institute of Standards and Technology (NIST) primary standard for volume or flow rate. If adjustments to the sampler's flow rate measurement system calibration are to be made in conjunction with an audit of the sampler's flow measurement system, such adjustments shall be made following the audit. Reference 2 in section 13.0 of this appendix contains additional guidance. 9.1.3 The sampler's flow rate measurement device shall be re-calibrated after electromechanical maintenance or transport of the sampler. 9.2 Flow rate calibration/verification procedure. 9.2.1 PM 2.5 a 2.5 9.2.2 The flow rate standard used for flow rate calibration shall have its own certification and be traceable to a NIST primary standard for volume or flow rate. A calibration relationship for the flow rate standard, e.g., an equation, curve, or family of curves relating actual flow rate (Q a 9.2.3 The sampler flow rate measurement device shall be calibrated or verified by removing the sampler inlet and connecting the flow rate standard to the sampler's downtube in accordance with the operation/instruction manual, such that the flow rate standard accurately measures the sampler's flow rate. The sampler operator shall first carry out a sampler leak check and confirm that the sampler passes the leak test and then verify that no leaks exist between the flow rate standard and the sampler. 9.2.4 The calibration relationship between the flow rate (in actual L/min) indicated by the flow rate standard and by the sampler's flow rate measurement device shall be established or verified in accordance with the sampler operation/instruction manual. Temperature and pressure corrections to the flow rate indicated by the flow rate standard may be required for certain types of flow rate standards. Calibration of the sampler's flow rate measurement device shall consist of at least three separate flow rate measurements (multipoint calibration) evenly spaced within the range of −10 percent to = 10 percent of the sampler's operational flow rate, section 7.4.1 of this appendix. Verification of the sampler's flow rate shall consist of one flow rate measurement at the sampler's operational flow rate. The sampler operation/instruction manual and reference 2 in section 13.0 of this appendix provide additional guidance. 9.2.5 If during a flow rate verification the reading of the sampler's flow rate indicator or measurement device differs by ±4 percent or more from the flow rate measured by the flow rate standard, a new multipoint calibration shall be performed and the flow rate verification must then be repeated. 9.2.6 Following the calibration or verification, the flow rate standard shall be removed from the sampler and the sampler inlet shall be reinstalled. Then the sampler's normal operating flow rate (in L/min) shall be determined with a clean filter in place. If the flow rate indicated by the sampler differs by ±2 percent or more from the required sampler flow rate, the sampler flow rate must be adjusted to the required flow rate, under section 7.4.1 of this appendix. 9.3 Periodic calibration or verification of the calibration of the sampler's ambient temperature, filter temperature, and barometric pressure measurement systems is also required. Reference 3 of section 13.0 of this appendix contains additional guidance. 10.0 PM 2.5 Measurement Procedure. 2.5 2.5 2.5 2.5 10.1 The sampler shall be set up, calibrated, and operated in accordance with the specific, detailed guidance provided in the specific sampler's operation or instruction manual and in accordance with a specific quality assurance program developed and established by the user, based on applicable supplementary guidance provided in reference 2 in section 13.0 of this appendix. 10.2 Each new sample filter shall be inspected for correct type and size and for pinholes, particles, and other imperfections. Unacceptable filters should be discarded. A unique identification number shall be assigned to each filter, and an information record shall be established for each filter. If the filter identification number is not or cannot be marked directly on the filter, alternative means, such as a number-identified storage container, must be established to maintain positive filter identification. 10.3 Each filter shall be conditioned in the conditioning environment in accordance with the requirements specified in section 8.2 of this appendix. 10.4 Following conditioning, each filter shall be weighed in accordance with the requirements specified in section 8.0 of this appendix and the presampling weight recorded with the filter identification number. 10.5 A numbered and preweighed filter shall be installed in the sampler following the instructions provided in the sampler operation or instruction manual. 10.6 The sampler shall be checked and prepared for sample collection in accordance with instructions provided in the sampler operation or instruction manual and with the specific quality assurance program established for the sampler by the user. 10.7 The sampler's timer shall be set to start the sample collection at the beginning of the desired sample period and stop the sample collection 24 hours later. 10.8 Information related to the sample collection (site location or identification number, sample date, filter identification number, and sampler model and serial number) shall be recorded and, if appropriate, entered into the sampler. 10.9 The sampler shall be allowed to collect the PM 2.5 10.10 Within 177 hours (7 days, 9 hours) of the end of the sample collection period, the filter, while still contained in the filter cassette, shall be carefully removed from the sampler, following the procedure provided in the sampler operation or instruction manual and the quality assurance program, and placed in a protective container. The protective container shall contain no loose material that could be transferred to the filter. The protective container shall hold the filter cassette securely such that the cover shall not come in contact with the filter's surfaces. Reference 2 in section 13.0 of this appendix contains additional information. 10.11 The total sample volume in actual m 3 10.12 All factors related to the validity or representativeness of the sample, such as sampler tampering or malfunctions, unusual meteorological conditions, construction activity, fires or dust storms, etc. shall be recorded as required by the local quality assurance program. The occurrence of a flag warning during a sample period shall not necessarily indicate an invalid sample but rather shall indicate the need for specific review of the QC data by a quality assurance officer to determine sample validity. 10.13 After retrieval from the sampler, the exposed filter containing the PM 2.5 10.14. The exposed filter containing the PM 2.5 10.15. The filter shall be reweighed immediately after conditioning in accordance with the requirements specified in section 8.0 of this appendix, and the postsampling weight shall be recorded with the filter identification number. 10.16 The PM 2.5 11.0 Sampler Maintenance. 12.0 Calculations 12.1 (a) The PM 2.5 PM 2.5 f i a where: PM 2.5 2.5 3 W f i 2.5 V a 3 Note: Total sample time must be between 1,380 and 1,500 minutes (23 and 25 hrs) for a fully valid PM 2.5 13.0 References. 1. Quality Assurance Handbook for Air Pollution Measurement Systems, Volume I, Principles. EPA/600/R-94/038a, April 1994. Available from CERI, ORD Publications, U.S. Environmental Protection Agency, 26 West Martin Luther King Drive, Cincinnati, Ohio 45268. 2. Quality Assurance Guidance Document 2.12. Monitoring PM 2.5 http://www.epa.gov/ttn/amtic/pmqainf.html. 3. Quality Assurance Handbook for Air Pollution Measurement Systems, Volume IV: Meteorological Measurements, (Revised Edition) EPA/600/R-94/038d, March, 1995. Available from CERI, ORD Publications, U.S. Environmental Protection Agency, 26 West Martin Luther King Drive, Cincinnati, Ohio 45268. 4. Military standard specification (mil. spec.) 8625F, Type II, Class 1 as listed in Department of Defense Index of Specifications and Standards (DODISS), available from DODSSP-Customer Service, Standardization Documents Order Desk, 700 Robbins Avenue, Building 4D, Philadelphia, PA 1911-5094. 14.0 Figures L-1 through L-30 to Appendix L. [62 FR 38714, July 18, 1997, as amended at 64 FR 19719, Apr. 22, 1999; 71 FR 61226, Oct. 17, 2006; 89 FR 16381, Mar. 6, 2024] Appendix M to Part 50 [Reserved] Appendix N to Part 50—Interpretation of the National Ambient Air Quality Standards for PM 2.5 1.0 General (a) This appendix explains the data handling conventions and computations necessary for determining when the national ambient air quality standards (NAAQS) for PM 2.5 2.5 2.5 2.5 i.e., 2.5 2.5 2.5 (b) Decisions to exclude, retain, or make adjustments to the data affected by exceptional events, including natural events, are made according to the requirements and process deadlines specified in §§ 50.1, 50.14 and 51.930 of this chapter. (c) The terms used in this appendix are defined as follows: Annual mean The Air Quality System (AQS) Collocated monitors 2.5 Combined site data record Creditable samples Daily values 2.5 Data substitution tests 2.5 2.5 Design values (DVs) (1) The 3-year average of PM 2.5 annual PM 2.5 NAAQS DV (2) The 3-year average of annual 98th percentile 24-hour average PM 2.5 24-hour (or daily) PM 2.5 NAAQS DV Eligible sites 2.5 2.5 Extra samples Make-up samples The maximum quarterly value data substitution test 2.5 The minimum quarterly value data substitution test 2.5 98th percentile 2.5 Primary monitors Quarter Quarterly data capture rate Scheduled PM 2.5 samples Seasonal sampling Suitable monitors 2.5 Test design values (TDV) 2.5 min max Year 2.0 Monitoring Considerations (a) Section 58.30 of this chapter provides special considerations for data comparisons to the annual PM 2.5 (b) Monitors meeting the network technical requirements detailed in § 58.11 of this chapter are suitable for comparison with the NAAQS for PM 2.5 (c) Section 58.12 of this chapter specifies the required minimum frequency of sampling for PM 2.5 3.0 Requirements for Data Use and Data Reporting for Comparisons With the NAAQS for PM 2.5 (a) Except as otherwise provided in this appendix, all valid FRM/FEM/ARM PM 2.5 (b) PM 2.5 3 2.5 2.5 (c) Twenty-four-hour average concentrations will be computed in AQS from submitted hourly PM 2.5 2.5 3 2.5 (d) All calculations shown in this appendix shall be implemented on a site-level basis. Site level concentration data shall be processed as follows: (1) The default dataset for PM 2.5 (2) Data for the primary monitors shall be augmented as much as possible with data from collocated monitors. If a valid daily value is not produced by the primary monitor for a particular day (scheduled or otherwise), but a value is available from a collocated monitor, then that collocated value shall be considered part of the combined site data record. If more than one collocated daily value is available, the average of those valid collocated values shall be used as the daily value. The data record resulting from this procedure is referred to as the “combined site data record.” (3) In certain circumstances, including but not limited to site closures or relocations, data from two nearby sites may be combined into a single site data record for the purpose of calculating a valid design value. The appropriate Regional Administrator may approve such site combinations if the Regional Administrator determines that the measured concentrations do not differ substantially between the two sites, taking into consideration factors such as distance between sites, spatial and temporal patterns in air quality, local emissions and meteorology, jurisdictional boundaries, and terrain features. (e) All daily values in a combined site data record are used in the calculations specified in this appendix; however, not all daily values are given credit towards data completeness requirements. Only creditable samples are given credit for data completeness. Creditable samples include daily values in the combined site record that are collected on scheduled sampling days and valid make-up samples taken for missed or invalidated samples on scheduled sampling days. Days are considered scheduled according to the required sampling frequency of the designated primary monitor with one exception. The exception is, if a collocated continuous FEM/ARM monitor has a more intensive sampling frequency than the primary FRM monitor, then samples contributed to the combined site record from that continuous FEM/ARM monitor are always considered scheduled and, hence, also creditable. Daily values in the combined site data record that are reported for nonscheduled days, but that are not valid make-up samples are referred to as extra samples. 4.0 Comparisons With the Annual and 24-Hour PM 2.5 4.1 Annual PM 2.5 (a) Levels of the primary and secondary annual PM 2.5 (b) Three years of valid annual means are required to produce a valid annual PM 2.5 2.5 2.5 2.5 (c) In the case of one, two, or three years that do not meet the completeness requirements of section 4.1(b) of this appendix and thus would normally not be useable for the calculation of a valid annual PM 2.5 2.5 (i) An annual PM 2.5 Procedure: 2.5 min 2.5 2.5 (ii) An annual PM 2.5 Procedure: 2.5 2.5 max 2.5 2.5 (d) An annual PM 2.5 (e) The equations for calculating the annual PM 2.5 4.2 Twenty-four-hour PM 2.5 (a) Levels of the primary and secondary 24-hour PM 2.5 (b) Three years of valid annual PM 2.5 2.5 2.5 (c) In the case of one, two, or three years that do not meet the completeness requirements of section 4.2(b) of this appendix and thus would normally not be useable for the calculation of a valid 24-hour PM 2.5 2.5 (i) A PM 2.5 Procedure: 2.5 2.5 max 2.5 2.5 (d) A 24-hour PM 2.5 (e) The procedures and equations for calculating the 24-hour PM 2.5 4.3 Rounding Conventions. For the purposes of comparing calculated PM 2.5 (a) Annual PM 2.5 3 (b) Twenty-four-hour PM 2.5 3 4.4 Equations for the Annual PM 2.5 (a) An annual mean value for PM 2.5 Where: X q,y n q x i q,y th (b) Equation 2 of this appendix is then used to calculate the site annual mean: Where: X y y y n Q,y X q,y q y (c) The annual PM 2.5 Where: X 2.5 X y y (d) The annual PM 2.5 2.5 4.5 Procedures and Equations for the 24-Hour PM 2.5 (a) When the data for a particular site and year meet the data completeness requirements in section 4.2 of this appendix, calculation of the 98th percentile is accomplished by the steps provided in this subsection. Table 1 of this appendix shall be used to identify annual 98th percentile values. Identification of annual 98th percentile values using the Table 1 procedure will be based on the creditable number of samples (as described below), rather than on the actual number of samples. Credit will not be granted for extra (non-creditable) samples. Extra samples, however, are candidates for selection as the annual 98th percentile. [The creditable number of samples will determine how deep to go into the data distribution, but all samples (creditable and extra) will be considered when making the percentile assignment.] The annual creditable number of samples is the sum of the four quarterly creditable number of samples. Procedure: y 0.98, y th Table 1 Annual number of creditable samples for year y y The 98th percentile for year y (P 0.98,y th n 1 to 50 1 51 to 100 2 101 to 150 3 151 to 200 4 201 to 250 5 251 to 300 6 301 to 350 7 351 to 366 8 (b) The 24-hour PM 2.5 0.98,y Where: P 0.98 2.5 P 0.98, y y (c) The 24-hour PM 2.5 [78 FR 3277, Jan. 15, 2013, as amended at 82 FR 14327, Mar. 20, 2017; 89 FR 16381, Mar. 6, 2024] Appendix O to Part 50—Reference Method for the Determination of Coarse Particulate Matter as PM 10-2.5 1.0 Applicability and Definition 1.1 This method provides for the measurement of the mass concentration of coarse particulate matter (PM 10-2.5 1.2 For the purpose of this method, PM 10-2.5 1.3 For this reference method, PM 10-2.5 10 2.5 10 10c 10 10c 10c 10 10 10-2.5 10c 2.5 1.4 The PM 10c 2.5 10c 2.5 10-2.5 1.5 Quality assessment procedures are provided in part 58, appendix A of this chapter. The quality assurance procedures and guidance provided in reference 1 in section 13 of this appendix, although written specifically for PM 2.5 10c 10-2.5 1.6 A method based on specific model PM 10c 2.5 (a) The PM 10c 2.5 (b) The method based on the specific samplers and associated operational procedures have been designated as a reference method in accordance with part 53 of this chapter. 1.7 PM 10-2.5 10-2.5 1.8 PM 2.5 10-2.5 2.5 1.9 PM 10c 10-2.5 10 (a) The PM 10c (b) Such PM 10c 10 10 10 2.0 Principle 2.1 Separate, collocated, electrically powered air samplers for PM 10c 2.5 10 2.5 10-2.5 2.2 Each PM 10c 2.5 10c 2.5 10c 2.5 10 2.5 3 10-2.5 10c 2.5 2.3 Most requirements for PM 10-2.5 2.5 3.0 PM 10-2.5 Measurement Range 3.1 Lower concentration limit. 3 2.5 2.5 10c 10-2.5 3.2 Upper concentration limit. 10c 10c 3 10-2.5 10-2.5 10 3.3 Sample period. 10-2.5 2.5 10c 4.0 Accuracy (bias) 4.1 Because the size, density, and volatility of the particles making up ambient particulate matter vary over wide ranges and the mass concentration of particles varies with particle size, it is difficult to define the accuracy of PM 10-2.5 10-2.5 10-2.5 4.2 Measurement system bias for monitoring data is assessed according to the procedures and schedule set forth in part 58, appendix A of this chapter. The goal for the measurement uncertainty (as bias) for monitoring data is defined in part 58, appendix A of this chapter as an upper 95 percent confidence limit for the absolute bias of 15 percent. Reference 1 in section 13 of this appendix provides additional information and guidance on flow rate accuracy audits and assessment of bias. 5.0 Precision 5.1 Tests to establish initial measurement precision for each sampler of the reference method sampler pair are specified as a part of the requirements for designation as a reference method under part 53 of this chapter. 5.2 Measurement system precision is assessed according to the procedures and schedule set forth in appendix A to part 58 of this chapter. The goal for acceptable measurement uncertainty, as precision, of monitoring data is defined in part 58, appendix A of this chapter as an upper 95 percent confidence limit for the coefficient of variation (CV) of 15 percent. Reference 1 in section 13 of this appendix provides additional information and guidance on this requirement. 6.0 Filters for PM 10c and PM 2.5 Sample Collection. 10c 2.5 7.0 Sampler. 10-2.5 10c 2.5 7.1 The PM 2.5 7.2 The PM 10c 2.5 7.2.1 The particle size separator specified in section 7.3.4 of appendix L to this part shall be eliminated and replaced by a downtube extension fabricated as specified in Figure O-1 of this appendix. 7.2.2 The sampler shall be identified as a PM 10c 7.2.3 The average temperature and average barometric pressure measured by the sampler during the sample period, as described in Table L-1 of appendix L to this part, need not be reported to EPA's AQS data base, as required by section 7.4.19 and Table L-1 of appendix L to this part, provided such measurements for the sample period determined by the associated PM 2.5 7.3 In addition to the operation/instruction manual required by section 7.4.18 of appendix L to this part for each sampler, supplemental operational instructions shall be provided for the simultaneous operation of the samplers as a pair to collect concurrent PM 10c 2.5 10-2.5 7.4 Capability for electrical interconnection of the samplers to simplify sample period programming and further ensure simultaneous operation is encouraged but not required. Any such capability for interconnection shall not supplant each sampler's capability to operate independently, as required by section 7 of appendix L of this part. 8.0 Filter Weighing 8.1 Conditioning and weighing for both PM 10c 2.5 8.2 Handling, conditioning, and weighing for both PM 10c 2.5 10c 2.5 10c 2.5 8.3 Due care shall be exercised to accurately maintain the paired relationship of each set of concurrently collected PM 10 2.5 9.0 Calibration. 10c 2.5 10.0 PM 10-2.5 10.1 The PM 10c 2.5 10.2 The measurement procedure for PM 10c 10c 2.5 10.3 The measurement procedure for PM 2.5 10.4 For the PM 10-2.5 10c 2.5 10.5 Retrieval, transport, and storage of each PM 10c 2.5 11.0 Sampler Maintenance. 10c 2.5 12.0 Calculations 12.1 Both concurrent PM 10c 2.5 10-2.5 12.2 The PM 10c Where: PM 10c 10c 3 W f i 10c V a 10c 3 Note: Total sample time must be between 1,380 and 1,500 minutes (23 and 25 hrs) for a fully valid PM 10c 12.3 The PM 2.5 12.4 The PM 10−2.5 3 13.0 Reference 1. Quality Assurance Guidance Document 2.12. Monitoring PM 2.5 www.epa.gov/ttn/amtic/pgqa.html. 14.0 Figures Figure O-1 is included as part of this appendix O. [71 FR 61230, Oct. 17, 2006] Appendix P to Part 50—Interpretation of the Primary and Secondary National Ambient Air Quality Standards for Ozone 1. General (a) This appendix explains the data handling conventions and computations necessary for determining whether the national 8-hour primary and secondary ambient air quality standards for ozone (O 3 3 3 3 3 (b) The terms used in this appendix are defined as follows: 8-hour average 3 Annual fourth-highest daily maximum Daily maximum 8-hour average concentration Design values i.e. O 3 monitoring season 3 Year 2. Primary and Secondary Ambient Air Quality Standards for Ozone 2.1 Data Reporting and Handling Conventions Computing 8-hour averages. 3 3 Daily maximum 8-hour average concentrations. 3 3 3 3 (b) An O 3 i.e. 2.2 Primary and Secondary Standard-related Summary Statistic The standard-related summary statistic is the annual fourth-highest daily maximum 8-hour O 3 3 2.3 Comparisons with the Primary and Secondary Ozone Standards (a) The primary and secondary O 3 3 (b) This comparison shall be based on three consecutive, complete calendar years of air quality monitoring data. This requirement is met for the 3-year period at a monitoring site if daily maximum 8-hour average concentrations are available for at least 90% of the days within the O 3 3 (c) Years with concentrations greater than the level of the standard shall be included even if they have less than complete data. Thus, in computing the 3-year average fourth maximum concentration, calendar years with less than 75% data completeness shall be included in the computation if the 3-year average fourth-highest 8-hour concentration is greater than the level of the standard. (d) Comparisons with the primary and secondary O 3 Example 1—Ambient Monitoring Site Attaining the Primary and Secondary O 3 Year Percent valid days (within the required monitoring season) 1st Highest daily max 8-hour Conc. (ppm) 2nd Highest daily max 8-hour Conc. (ppm) 3rd Highest daily max 8-hour Conc. (ppm) 4th Highest daily max 8-hour Conc. (ppm) 5th Highest daily max 8-hour Conc. (ppm) 2004 100 0.092 0.090 0.085 0.079 0.078 2005 96 0.084 0.083 0.075 0.072 0.070 2006 98 0.080 0.079 0.077 0.076 0.060 Average 98 0.075 (1) As shown in Example 1, this monitoring site meets the primary and secondary O 3 3 i.e. Example 2—Ambient Monitoring Site Failing to Meet the Primary and Secondary O 3 Year Percent valid days (within the required monitoring season) 1st Highest daily max 8-hour Conc. (ppm) 2nd Highest daily max 8-hour Conc. (ppm) 3rd Highest daily max 8-hour Conc. (ppm) 4th Highest daily max 8-hour Conc. (ppm) 5th Highest daily max 8-hour Conc. (ppm) 2004 96 0.105 0.103 0.103 0.103 0.102 2005 74 0.104 0.103 0.092 0.091 0.088 2006 98 0.103 0.101 0.101 0.095 0.094 Average 89 0.096 As shown in Example 2, the primary and secondary O 3 3 i.e. 3. Design Values for Primary and Secondary Ambient Air Quality Standards for Ozone The air quality design value at a monitoring site is defined as that concentration that when reduced to the level of the standard ensures that the site meets the standard. For a concentration-based standard, the air quality design value is simply the standard-related test statistic. Thus, for the primary and secondary standards, the 3-year average annual fourth-highest daily maximum 8-hour average O 3 [73 FR 16511, Mar. 27, 2008] Appendix Q to Part 50—Reference Method for the Determination of Lead in Particulate Matter as PM 10 This Federal Reference Method (FRM) draws heavily from the specific analytical protocols used by the U.S. EPA. 1. Applicability and Principle 1.1 This method provides for the measurement of the lead (Pb) concentration in particulate matter that is 10 micrometers or less (PM 10 10 3 10 10c 10 1.2 For this reference method, PM 10 10c 10c 10−2.5 10c 2.5 3 1.3 The FRM will serve as the basis for approving Federal Equivalent Methods (FEMs) as specified in 40 CFR Part 53 (Reference and Equivalent Methods). This FRM specifically applies to the analysis of Pb in PM 10 10c 1.4 The PM 10c 10 10 1.5 Quality assurance (QA) procedures for the collection of monitoring data are contained in Part 58, appendix A. 2. PM 10 Pb Measurement Range and Detection Limit. 3 3 2.1 EDXRF Pb Measurement Range. 3 2 2 3 2.2 Detection Limit (DL). 2 3 2 3 3. Factors Affecting Bias and Precision of Lead Determination by EDXRF 3.1 Filter Deposit. 2 2 10 10c 3 2 10c 10C 3.2 Spectral Interferences and Spectral Overlap. α α α β γ 3.3 Particle Size Effects and Attenuation Correction Factors. 10 4. Precision 4.1 Measurement system precision is assessed according to the procedures set forth in appendix A to part 58. Measurement method precision is assessed from collocated sampling and analysis. The goal for acceptable measurement uncertainty, as precision, is defined as an upper 90 percent confidence limit for the coefficient of variation (CV) of 20 percent. 5. Bias 5.1 Measurement system bias for monitoring data is assessed according to the procedures set forth in appendix A of part 58. The bias is assessed through an audit using spiked filters. The goal for measurement bias is defined as an upper 95 percent confidence limit for the absolute bias of 15 percent. 6. Measurement of PTFE Filters by EDXRF 6.1 Sampling 6.1.1 Low-Volume PM 10c Sampler. 10c 10 6.1.2 PTFE Filters and Filter Acceptance Testing. 10c 2.5 2 2 6.1.2.1 Filter Blanks. 6.2 Analysis. 6.2.1 EDXRF Analysis Instrument. www.thermo.com http://www.spectro.com http://www.xenemetrix.com http://www.panalytical.com 1 1 6.2.2 Thin film standards. 2 6.2.3 Filter Preparation. 2 6.2.4 Calibration. i.e. 2 2 See 6.2.4.1 Spectral Peak Fitting. 6.2.4.2 Background Measurement and Correction. 7. Calculation. 7.1 PM 10 Pb concentrations. 10 3 Where, M Pb 3 C Pb 2 A is the filter deposit area in cm 2 V LC 10c 3 7.2 PM 10 Pb Uncertainty Calculations. The principal contributors to total uncertainty of XRF values include: field sampling; filter deposit area; XRF calibration; attenuation or loss of the x-ray signals due to the other components of the particulate sample; and determination of the Pb X-ray emission peak area by curve fitting. See reference 12 for a detailed discussion of how uncertainties are similarly calculated for the PM 2.5 The model for calculating total uncertainty is: δ tot δ f 2 δ a 2 δ c 2 δ v 2 1/2 Where, δ f δ a δ c δ v 8. References 1. Inorganic Compendium Method IO-3.3; Determination of Metals in Ambient Particulate Matter Using X-Ray Fluorescence (XRF) Spectroscopy; U.S. Environmental Protection Agency, Cincinnati, OH 45268. EPA/625/R-96/010a. June 1999. 2. Jenkins, R., Gould, R.W., and Gedcke, D. Quantitative X-ray Spectrometry: Second Edition. Marcel Dekker, Inc., New York, NY. 1995. 3. Jenkins, R. X-Ray Fluorescence Spectrometry: Second Edition in Chemical Analysis, a Series of Monographs on Analytical Chemistry and Its Applications, Volume 152. Editor J.D.Winefordner; John Wiley & Sons, Inc., New York, NY. 1999. 4. Dzubay, T.G. X-ray Fluorescence Analysis of Environmental Samples, Ann Arbor Science Publishers Inc., 1977. 5. Code of Federal Regulations (CFR) 40, Part 136, Appendix B; Definition and Procedure for the Determination of the Method Detection Limit—Revision 1.1. 6. Drane, E.A, Rickel, D.G., and Courtney, W.J., “Computer Code for Analysis X-Ray Fluorescence Spectra of Airborne Particulate Matter,” in Advances in X-Ray Analysis, J.R. Rhodes, Ed., Plenum Publishing Corporation, New York, NY, p. 23 (1980). 7. Analysis of Energy-Dispersive X-ray Spectra of Ambient Aerosols with Shapes Optimization, Guidance Document; TR-WDE-06-02; prepared under contract EP-D-05-065 for the U.S. Environmental Protection Agency, National Exposure Research Laboratory. March 2006. 8. Billiet, J., Dams, R., and Hoste, J. (1980) Multielement Thin Film Standards for XRF Analysis, X-Ray Spectrometry, 9(4): 206-211. 9. Bonner, N.A.; Bazan, F.; and Camp, D.C. (1973). Elemental analysis of air filter samples using x-ray fluorescence. Report No. UCRL-51388. Prepared for U.S. Atomic Energy Commission, by Univ. of Calif., Lawrence Livermore Laboratory, Livermore, CA. 10. Dzubay, T.G.; Lamothe, P.J.; and Yoshuda, H. (1977). Polymer films as calibration standards for X-ray fluorescence analysis. Adv. X-Ray Anal., 20:411. 11. Giauque, R.D.; Garrett, R.B.; and Goda, L.Y. (1977). Calibration of energy-dispersive X-ray spectrometers for analysis of thin environmental samples. In X-Ray Fluorescence Analysis of Environmental Samples, T.G. Dzubay, Ed., Ann Arbor Science Publishers, Ann Arbor, MI, pp. 153-181. 12. Harmonization of Interlaboratory X-ray Fluorescence Measurement Uncertainties, Detailed Discussion Paper; August 4, 2006; prepared for the Office of Air Quality Planning and Standards under EPA contract 68-D-03-038. http://www.epa.gov/ttn/amtic/files/ambient/pm25/spec/xrfdet.pdf. [73 FR 67052, Nov. 12, 2008] Appendix R to Part 50—Interpretation of the National Ambient Air Quality Standards for Lead 1. General. (a) This appendix explains the data handling conventions and computations necessary for determining when the primary and secondary national ambient air quality standards (NAAQS) for lead (Pb) specified in § 50.16 are met. The NAAQS indicator for Pb is defined as: lead and its compounds, measured as elemental lead in total suspended particulate (Pb-TSP), sampled and analyzed by a Federal reference method (FRM) based on appendix G to this part or by a Federal equivalent method (FEM) designated in accordance with part 53 of this chapter. Although Pb-TSP is the lead NAAQS indicator, surrogate Pb-TSP concentrations shall also be used for NAAQS comparisons; specifically, valid surrogate Pb-TSP data are concentration data for lead and its compounds, measured as elemental lead, in particles with an aerodynamic size of 10 microns or less (Pb-PM 10 i.e. 10 i.e. 10 (b) Whether to exclude, retain, or make adjustments to the data affected by exceptional events, including natural events, is determined by the requirements and process deadlines specified in §§ 50.1, 50.14, and 51.930 of this chapter. (c) The terms used in this appendix are defined as follows: Annual monitoring network plan Creditable samples Daily values 10 Design value i.e. 10 i.e. Extra samples 10 Make-up samples 10 Monthly mean 10 i.e. Parameter 10 Pollutant Occurrence Code (POC) Scheduled sampling day Three-month means Year 2. Use of Pb-PM 10 Data as Surrogate Pb-TSP Data. (a) As stipulated in section 2.10 of Appendix C to 40 CFR part 58, at some mandatory Pb monitoring locations, monitoring agencies are required to sample for Pb as Pb-TSP, and at other mandatory Pb monitoring sites, monitoring agencies are permitted to monitor for Pb-PM 10 10 10 (i) Whenever a valid 3-month Pb-PM 10 10 (ii) Otherwise ( i.e. 10 (A) If a valid 3-month Pb-TSP mean exists, then it will be the site-level mean for that (site's) 3-month period, or (B) If a valid 3-month Pb-TSP mean does not exist, then there is no valid 3-month site mean for that period (even if a valid non-violating 3-month Pb-PM 10 (b) As noted in section 1(a) of this appendix, FRM/FEM Pb-PM 10 i.e. 3. Requirements for Data Used for Comparisons With the Pb NAAQS and Data Reporting Considerations. (a) All valid FRM/FEM Pb-TSP data and all valid FRM/FEM Pb-PM 10 10 i.e. (b) Pb-TSP and Pb-PM 10 3 10 i.e. 10 (c) At each monitoring location (site), Pb-TSP and Pb-PM 10 i.e. (d) Daily values for sites will be selected for a site on a size cut (Pb-TSP or Pb-PM 10 10 (i) The starting dataset for a site-parameter shall consist of the measured daily concentrations recorded from the designated primary FRM/FEM monitor for that parameter. The primary monitor for each parameter shall be designated in the appropriate state or local agency annual Monitoring Network Plan. If no primary monitor is designated, the Administrator will select which monitor to treat as primary. All daily values produced by the primary sampler are considered part of the site-parameter data record ( i.e. 10 10 i.e. (ii) Data for the primary monitor for each parameter shall be augmented as much as possible with data from collocated (same parameter) FRM/FEM monitors. If a valid 24-hour measurement is not produced from the primary monitor for a particular day (scheduled or otherwise), but a valid sample is generated by a collocated (same parameter) FRM/FEM instrument, then that collocated value shall be considered part of the site-parameter data record ( i.e. (e) All daily values in the composite site-parameter record are used in monthly mean calculations. However, not all daily values are given credit towards data completeness requirements. Only “creditable” samples are given credit for data completeness. Creditable samples include valid samples on scheduled sampling days and valid make-up samples. All other types of daily values are referred to as “extra” samples. Make-up samples taken in the (first week of the) month after the one in which the miss/void occurred will be credited for data capture in the month of the miss/void but will be included in the month actually taken when computing monthly means. For example, if a make-up sample was taken in February to replace a missed sample scheduled for January, the make-up concentration would be included in the February monthly mean but the sample credited in the January data capture rate. 4. Comparisons With the Pb NAAQS. (a) The Pb NAAQS is met at a monitoring site when the identified design value is valid and less than or equal to 0.15 micrograms per cubic meter (µg/m 3 i.e. 3 (b) The Pb NAAQS is violated at a monitoring site when the identified design value is valid and is greater than 0.15 µg/m 3 10 3 i.e. (c)(i) A 3-month parameter mean is considered valid ( i.e. i.e. 10 10 10 (ii) A 3-month parameter mean that does not have at least 75 percent data capture and thus is not considered valid under 4(c)(i) shall be considered valid (and complete) if it passes either of the two following “data substitution” tests, one such test for validating an above NAAQS-level ( i.e. 10 i.e. i.e. i.e. (A) The “above NAAQS level” test is as follows: Data substitution will be done in each month of the 3-month period that has less than 75 percent data capture; monthly capture rates are temporarily rounded to integers (zero decimals) for this evaluation. If by substituting the lowest reported daily value for that month (year non-specific; e.g., for January) over the 38-month design value period in question for missing scheduled data in the deficient months (substituting only enough to meet the 75 percent data capture minimum), the computation yields a recalculated test 3-month parameter mean concentration above the level of the standard, then the 3-month period is deemed to have passed the diagnostic test and the level of the standard is deemed to have been exceeded in that 3-month period. As noted in section 4(c)(ii), in such a case, the 3-month parameter mean of the data actually reported, not the recalculated (“test”) result including the low values, shall be used to determine the design value. (B) The “below NAAQS level” test is as follows: Data substitution will be performed for each month of the 3-month period that has less than 75 percent but at least 50 percent data capture; if any month has less than 50% data capture then the 3-month mean can not utilize this substitution test. Also, incomplete 3-month Pb-PM 10 i.e. 3 (d) Months that do not meet the completeness criteria stated in 4(c)(i) or 4(c)(ii), and design values that do not meet the completeness criteria stated in 4(a) or 4(b), may also be considered valid (and complete) with the approval of, or at the initiative of, the Administrator, who may consider factors such as monitoring site closures/moves, monitoring diligence, the consistency and levels of the valid concentration measurements that are available, and nearby concentrations in determining whether to use such data. (e) The site-level design value for a 38-month period (three calendar years plus two previous months) is identified from the available (between one and 36) valid 3-month site means. In a situation where there are valid 3-month means for both parameters (Pb-TSP and Pb-PM 10 10 i.e. 10 (f) The procedures for calculating monthly means and 3-month means, and identifying Pb design values are given in section 6 of this appendix. 5. Rounding Conventions. (a) Monthly means and monthly data capture rates are not rounded. (b) Three-month means shall be rounded to the nearest hundredth µg/m 3 (c) Because a Pb design value is simply a (highest) 3-month mean and because the NAAQS level is stated to two decimal places, no additional rounding beyond what is specified for 3-month means is required before a design value is compared to the NAAQS. 6. Procedures and Equations for the Pb NAAQS. (a)(i) A monthly mean value for Pb-TSP (or Pb-PM 10 Where: X m,y,s n m X i,m,y,s th (a)(ii) The Administrator may at his discretion use the following alternate approach to calculating the monthly mean concentration if the number of extra sampling days during a month is greater than the number of successfully completed scheduled and make-up sample days in that month. In exercising his discretion, the Administrator will consider whether the approach specified in 6(a)(i) might in the Administrator's judgment result in an unrepresentative value for the monthly mean concentration. This provision is to protect the integrity of the monthly and 3-month mean concentration values in situations in which, by intention or otherwise, extra sampling days are concentrated in a period during which ambient concentrations are particularly high or low. The alternate approach is to average all extra and make-up samples (in the given month) taken after each scheduled sampling day (“Day X”) and before the next scheduled sampling day (e.g., “Day X + 6”, in the case of one-in-six sampling) with the sample taken on Day X (assuming valid data was obtained on the scheduled sampling day), and then averaging these averages to calculate the monthly mean. This approach has the effect of giving approximately equal weight to periods during a month that have equal number of days, regardless of how many samples were actually obtained during the periods, thus mitigating the potential for the monthly mean to be distorted. The first day of scheduled sampling typically will not fall on the first day of the calendar month, and there may be make-up and/or extra samples (in that same calendar month) preceding the first scheduled day of the month. These samples will not be shifted into the previous month's mean concentration, but rather will stay associated with their actual calendar month as follows. Any extra and make-up samples taken in a month before the first scheduled sampling day of the month will be associated with and averaged with the last scheduled sampling day of that same month. (b) Three-month parameter means are determined by averaging three consecutive monthly means of the same parameter using Equation 2 of this appendix. Where: X m1, m2, m3 s n m X m, y z, s (c) Three-month site means are determined from available 3-month parameter means according to the hierarchy established in 2(a) of this appendix. (d) The site-level Pb design value is the highest valid 3-month site-level mean over the most recent 38-month period ( i.e. [73 FR 67054, Nov. 12, 2008] Appendix S to Part 50—Interpretation of the Primary National Ambient Air Quality Standards for Oxides of Nitrogen (Nitrogen Dioxide) 1. General (a) This appendix explains the data handling conventions and computations necessary for determining when the primary national ambient air quality standards for oxides of nitrogen as measured by nitrogen dioxide (“NO 2 2 2 2 (b) Whether to exclude, retain, or make adjustments to the data affected by exceptional events, including natural events, is determined by the requirements and process deadlines specified in 50.1, 50.14 and 51.930 of this chapter. (c) The terms used in this appendix are defined as follows: Annual mean Daily maximum 1-hour values 2 2 Design values i.e. (1) The annual mean value for a monitoring site for one year (referred to as the “annual primary standard design value”). (2) The 3-year average of annual 98th percentile daily maximum 1-hour values for a monitoring site (referred to as the “1-hour primary standard design value”). 98th percentile daily maximum 1-hour value Quarter Year 2. Requirements for Data Used for Comparisons With the NO 2 (a) All valid FRM/FEM NO 2 (b) When two or more NO 2 (c) Hourly NO 2 3. Comparisons With the NO 2 3.1 The Annual Primary NO 2 (a) The annual primary NO 2 (b) An annual primary standard design value is valid when at least 75 percent of the hours in the year are reported. (c) An annual primary standard design value based on data that do not meet the completeness criteria stated in section 3.1(b) may also be considered valid with the approval of, or at the initiative of, the Administrator, who may consider factors such as monitoring site closures/moves, monitoring diligence, the consistency and levels of the valid concentration measurements that are available, and nearby concentrations in determining whether to use such data. (d) The procedures for calculating the annual primary standard design values are given in section 5.1 of this appendix. 3.2 The 1-hour Primary NO 2 (a) The 1-hour primary NO 2 (b) An NO 2 (c) In the case of one, two, or three years that do not meet the completeness requirements of section 3.2(b) of this appendix and thus would normally not be useable for the calculation of a valid 3-year 1-hour primary standard design value, the 3-year 1-hour primary standard design value shall nevertheless be considered valid if one of the following conditions is true. (i) At least 75 percent of the days in each quarter of each of three consecutive years have at least one reported hourly value, and the design value calculated according to the procedures specified in section 5.2 is above the level of the primary 1-hour standard. (ii)(A) A 1-hour primary standard design value that is below the level of the NAAQS can be validated if the substitution test in section 3.2(c)(ii)(B) results in a “test design value” that is below the level of the NAAQS. The test substitutes actual “high” reported daily maximum 1-hour values from the same site at about the same time of the year (specifically, in the same calendar quarter) for unknown values that were not successfully measured. Note that the test is merely diagnostic in nature, intended to confirm that there is a very high likelihood that the original design value (the one with less than 75 percent data capture of hours by day and of days by quarter) reflects the true under-NAAQS-level status for that 3-year period; the result of this data substitution test (the “test design value”, as defined in section 3.2(c)(ii)(B)) is not considered the actual design value. For this test, substitution is permitted only if there are at least 200 days across the three matching quarters of the three years under consideration (which is about 75 percent of all possible daily values in those three quarters) for which 75 percent of the hours in the day, including State-flagged data affected by exceptional events which have been approved for exclusion by the Administrator, have reported concentrations. However, maximum 1-hour values from days with less than 75 percent of the hours reported shall also be considered in identifying the high value to be used for substitution. (B) The substitution test is as follows: (iii)(A) A 1-hour primary standard design value that is above the level of the NAAQS can be validated if the substitution test in section 3.2(c)(iii)(B) results in a “test design value” that is above the level of the NAAQS. The test substitutes actual “low” reported daily maximum 1-hour values from the same site at about the same time of the year (specifically, in the same three months of the calendar) for unknown values that were not successfully measured. Note that the test is merely diagnostic in nature, intended to confirm that there is a very high likelihood that the original design value (the one with less than 75 percent data capture of hours by day and of days by quarter) reflects the true above-NAAQS-level status for that 3-year period; the result of this data substitution test (the “test design value”, as defined in section 3.2(c)(iii)(B)) is not considered the actual design value. For this test, substitution is permitted only if there are a minimum number of available daily data points from which to identify the low quarter-specific daily maximum 1-hour values, specifically if there are at least 200 days across the three matching quarters of the three years under consideration (which is about 75 percent of all possible daily values in those three quarters) for which 75 percent of the hours in the day have reported concentrations. Only days with at least 75 percent of the hours reported shall be considered in identifying the low value to be used for substitution. (B) The substitution test is as follows: Data substitution will be performed in all quarter periods that have less than 75 percent data capture. Identify for each quarter (e.g., January-March) the lowest reported daily maximum 1-hour value for that quarter, looking across those three months of all three years under consideration. All daily maximum 1-hour values from all days with at least 75 percent capture in the quarter period shall be considered when identifying this lowest value. If after substituting the lowest reported daily maximum 1-hour value for a quarter for as much of the missing daily data in the matching deficient quarter(s) as is needed to make them 75 percent complete, the procedure in section 5.2 yields a recalculated 3-year 1-hour standard “test design value” above the level of the standard, then the 1-hour primary standard design value is deemed to have passed the diagnostic test and is valid, and the level of the standard is deemed to have been exceeded in that 3-year period. As noted in section 3.2(c)(i), in such a case, the 3-year design value based on the data actually reported, not the “test design value”, shall be used as the valid design value. (d) A 1-hour primary standard design value based on data that do not meet the completeness criteria stated in 3.2(b) and also do not satisfy section 3.2(c), may also be considered valid with the approval of, or at the initiative of, the Administrator, who may consider factors such as monitoring site closures/moves, monitoring diligence, the consistency and levels of the valid concentration measurements that are available, and nearby concentrations in determining whether to use such data. (e) The procedures for calculating the 1-hour primary standard design values are given in section 5.2 of this appendix. 4. Rounding Conventions 4.1 Rounding Conventions for the Annual Primary NO 2 (a) Hourly NO 2 (b) The annual primary standard design value is calculated pursuant to section 5.1 and then rounded to the nearest whole number or 1 ppb (decimals 0.5 and greater are rounded up to the nearest whole number, and any decimal lower than 0.5 is rounded down to the nearest whole number). 4.2 Rounding Conventions for the 1-hour Primary NO 2 (a) Hourly NO 2 (b) Daily maximum 1-hour values are not rounded. (c) The 1-hour primary standard design value is calculated pursuant to section 5.2 and then rounded to the nearest whole number or 1 ppb (decimals 0.5 and greater are rounded up to the nearest whole number, and any decimal lower than 0.5 is rounded down to the nearest whole number). 5. Calculation Procedures for the Primary NO 2 5.1 Procedures for the Annual Primary NO 2 (a) When the data for a site and year meet the data completeness requirements in section 3.1(b) of this appendix, or if the Administrator exercises the discretionary authority in section 3.1(c), the annual mean is simply the arithmetic average of all of the reported 1-hour values. (b) The annual primary standard design value for a site is the valid annual mean rounded according to the conventions in section 4.1. 5.2 Calculation Procedures for the 1-hour Primary NO 2 (a) Procedure for identifying annual 98th percentile values. (i) The annual 98th percentile value for a year is the higher of the two values resulting from the following two procedures. (1) Procedure 1. (A) For the year, determine the number of days with at least 75 percent of the hourly values reported including State-flagged data affected by exceptional events which have been approved for exclusion by the Administrator. (B) For the year, from only the days with at least 75 percent of the hourly values reported, select from each day the maximum hourly value excluding State-flagged data affected by exceptional events which have been approved for exclusion by the Administrator. (C) Sort all these daily maximum hourly values from a particular site and year by descending value. (For example: (x[1], x[2], x[3], * * *, x[n]). In this case, x[1] is the largest number and x[n] is the smallest value.) The 98th percentile is determined from this sorted series of daily values which is ordered from the highest to the lowest number. Using the left column of Table 1, determine the appropriate range ( i.e., y 0.98, y (2) Procedure 2. (A) For the year, determine the number of days with at least one hourly value reported including State-flagged data affected by exceptional events which have been approved for exclusion by the Administrator. (B) For the year, from all the days with at least one hourly value reported, select from each day the maximum hourly value excluding State-flagged data affected by exceptional events which have been approved for exclusion by the Administrator. (C) Sort all these daily maximum values from a particular site and year by descending value. (For example: (x[1], x[2], x[3], * * *, x[n]). In this case, x[1] is the largest number and x[n] is the smallest value.) The 98th percentile is determined from this sorted series of daily values which is ordered from the highest to the lowest number. Using the left column of Table 1, determine the appropriate range ( i.e., y 0.98, y (b) The 1-hour primary standard design value for a site is mean of the three annual 98th percentile values, rounded according to the conventions in section 4. Table 1 Annual number y P 0.98, y 1-50 1 51-100 2 101-150 3 151-200 4 201-250 5 251-300 6 301-350 7 351-366 8 [75 FR 6532, Feb. 9, 2010] Appendix T to Part 50—Interpretation of the Primary and Secondary National Ambient Air Quality Standards for Oxides of Sulfur (Sulfur Dioxide) 1. General (a) This appendix explains the data handling conventions and computations necessary for determining when the primary and secondary national ambient air quality standards for Oxides of Sulfur as measured by Sulfur Dioxide (“SO 2 2 2 2 (b) Decisions to exclude, retain, or make adjustments to the data affected by exceptional events, including natural events, are made according to the requirements and process deadlines specified in §§ 50.1, 50.14 and 51.930 of this chapter. (c) The terms used in this appendix are defined as follows: Annual mean Daily maximum 1-hour values 2 2 Daily mean values 2 2 Design values i.e., 99th percentile daily maximum 1-hour value Pollutant Occurrence Code (POC) etc. Quarter Year 2. Requirements for Data Used for Comparisons With the SO 2 (a) All valid FRM/FEM SO 2 (b) Data from two or more monitors from the same year at the same site reported to EPA under distinct Pollutant Occurrence Codes shall not be combined in an attempt to meet data completeness requirements. The Administrator will combine annual 99th percentile daily maximum concentration values from different monitors in different years, selected as described here, for the purpose of developing a valid 1-hour primary standard design value. If more than one of the monitors meets the completeness requirement for all four quarters of a year, the steps specified in section 5.1(a) of this appendix shall be applied to the data from the monitor with the highest average of the four quarterly completeness values to derive a valid annual 99th percentile daily maximum concentration. If no monitor is complete for all four quarters in a year, the steps specified in sections 3.1(c) and 5.1(a) of this appendix shall be applied to the data from the monitor with the highest average of the four quarterly completeness values in an attempt to derive a valid annual 99th percentile daily maximum concentration. Similarly, the Administrator will combine annual means from different monitors in different years, selected as described here, for the purpose of developing a valid annual secondary standard design value. If more than one of the monitors meets the completeness requirement for all four quarters of a year, the steps specified in section 5.2(a) of this appendix shall be applied to the data from the monitor with the highest average of the four quarterly completeness values to derive a valid annual mean. If no monitor is complete for all four quarters in a year, the steps specified in sections 3.2(c) and 5.2(a) of this appendix shall be applied to the data from the monitor with the highest average of the four quarterly completeness values in an attempt to derive a valid annual mean. This paragraph does not prohibit a monitoring agency from making a local designation of one physical monitor as the primary monitor for a Pollutant Occurrence Code and substituting the 1-hour data from a second physical monitor whenever a valid concentration value is not obtained from the primary monitor; if a monitoring agency substitutes data in this manner, each substituted value must be accompanied by an AQS qualifier code indicating that substitution with a value from a second physical monitor has taken place. (c) Hourly SO 2 3. Comparisons With the NAAQS 3.1 Comparisons With the 1-Hour Primary SO 2 (a) The 1-hour primary SO 2 (b) An SO 2 (c) In the case of one, two, or three years that do not meet the completeness requirements of section 3.1(b) of this appendix and thus would normally not be useable for the calculation of a valid 3-year 1-hour primary standard design value, the 3-year 1-hour primary standard design value shall nevertheless be considered valid if one of the following conditions is true. (i) At least 75 percent of the days in each quarter of each of three consecutive years have at least one reported hourly value, and the design value calculated according to the procedures specified in section 5.1 is above the level of the primary 1-hour standard. (ii)(A) A 1-hour primary standard design value that is equal to or below the level of the NAAQS can be validated if the substitution test in section 3.1(c)(ii)(B) of this appendix results in a “test design value” that is below the level of the NAAQS. The test substitutes actual “high” reported daily maximum 1-hour values from the same site at about the same time of the year (specifically, in the same calendar quarter) for unknown values that were not successfully measured. Note (B) The substitution test is as follows: Data substitution will be performed in all quarter periods that have less than 75 percent data capture but at least 50 percent data capture, including State-flagged data affected by exceptional events which have been approved for exclusion by the Administrator; if any quarter has less than 50 percent data capture then this substitution test cannot be used. Identify for each quarter ( e.g., (iii)(A) A 1-hour primary standard design value that is above the level of the NAAQS can be validated if the substitution test in section 3.1(c)(iii)(B) of this appendix results in a “test design value” that is above the level of the NAAQS. The test substitutes actual “low” reported daily maximum 1-hour values from the same site at about the same time of the year (specifically, in the same three months of the calendar) for unknown hourly values that were not successfully measured. Note that the test is merely diagnostic in nature, intended to confirm that there is a very high likelihood that the original design value (the one with less than 75 percent data capture of hours by day and of days by quarter) reflects the true above-NAAQS-level status for that 3-year period; the result of this data substitution test (the “test design value,” as defined in section 3.1(c)(iii)(B) of this appendix) is not considered the actual design value. For this test, substitution is permitted only if there are a minimum number of available daily data points from which to identify the low quarter-specific daily maximum 1-hour values, specifically if there are at least 200 days across the three matching quarters of the three years under consideration (which is about 75 percent of all possible daily values in those three quarters) for which 75 percent of the hours in the day have reported concentrations. Only days with at least 75 percent of the hours reported shall be considered in identifying the low value to be used for substitution. (B) The substitution test is as follows: Data substitution will be performed in all quarter periods that have less than 75 percent data capture. Identify for each quarter ( e.g., (d) A 1-hour primary standard design value based on data that do not meet the completeness criteria stated in section 3.1(b) of this appendix and also do not satisfy section 3.1(c) of this appendix, may also be considered valid with the approval of, or at the initiative of, the Administrator, who may consider factors such as monitoring site closures/moves, monitoring diligence, the consistency and levels of the valid concentration measurements that are available, and nearby concentrations in determining whether to use such data. (e) The procedures for calculating the 1-hour primary standard design values are given in section 5.1 of this appendix. 3.2 Comparisons With the Annual Secondary SO 2 (a) The annual secondary SO 2 (b) An SO 2 (c) In the case of one, two, or three years that do not meet the completeness requirements of section 3.2(b) of this appendix and thus would normally not be useable for the calculation of a valid 3-year annual secondary standard design value, the 3-year annual secondary standard design value shall nevertheless be considered valid if one of the following conditions is true. (i) At least 75 percent of the days in each quarter of each of three consecutive years have at least one reported hourly value, and the design value calculated according to the procedures specified in section 5.2 of this appendix is above the level of the secondary annual standard. (ii)(A) An annual secondary standard design value that is equal to or below the level of the NAAQS can be validated if the substitution test in section 3.2(c)(ii)(B) of this appendix results in a “test design value” that is below the level of the NAAQS. The test substitutes actual “high” reported daily mean values from the same site at about the same time of the year (specifically, in the same calendar quarter) for unknown or incomplete (less than 75 percent of hours reported) daily mean values. Note (B) The substitution test is as follows: Data substitution will be performed in all quarter periods that have less than 75 percent data capture but at least 50 percent data capture, including State-flagged data affected by exceptional events which have been approved for exclusion by the Administrator; if any quarter has less than 50 percent data capture then this substitution test cannot be used. Identify for each quarter ( e.g., (iii)(A) An annual secondary standard design value that is above the level of the NAAQS can be validated if the substitution test in section 3.2(c)(iii)(B) of this appendix results in a “test design value” that is above the level of the NAAQS. The test substitutes actual “low” reported daily mean values from the same site at about the same time of the year (specifically, in the same three months of the calendar) for unknown or incomplete (less than 75 percent of hours reported) daily mean values. Note that the test is merely diagnostic in nature, intended to confirm that there is a very high likelihood that the original design value (the one with less than 75 percent data capture of hours by day and of days by quarter) reflects the true above-NAAQS-level status for that 3-year period; the result of this data substitution test (the “test design value,” as defined in section 3.2(c)(iii)(B) of this appendix) is not considered the actual design value. For this test, substitution is permitted only if there are a minimum number of valid daily mean values from which to identify the low quarter-specific daily mean values, specifically if there are at least 200 days across the three matching quarters of the three years under consideration (which is about 75 percent of all possible daily values in those three quarters) for which 75 percent of the hours in the day have reported concentrations. Only days with at least 75 percent of the hours reported shall be considered in identifying the low daily mean value to be used for substitution. (B) The substitution test is as follows: Data substitution will be performed in all quarter periods that have less than 75 percent data capture. Identify for each quarter ( e.g., (d) An annual secondary standard design value based on data that do not meet the completeness criteria stated in section 3.2(b) of this appendix and also do not satisfy section 3.2(c) of this appendix, may also be considered valid with the approval of, or at the initiative of, the Administrator, who may consider factors such as monitoring site closures/moves, monitoring diligence, the consistency and levels of the valid concentration measurements that are available, and nearby concentrations in determining whether to use such data. (e) The procedures for calculating the annual secondary standard design values are given in section 5.2 of this appendix. 4. Rounding Conventions 4.1 Rounding Conventions for the 1-Hour Primary SO 2 (a) Hourly SO 2 (b) Daily maximum 1-hour values and, therefore, the annual 99th percentile of those daily values are not rounded. (c) The 1-hour primary standard design value is calculated pursuant to section 5.1 of this appendix and then rounded to the nearest whole number or 1 ppb (decimals 0.5 and greater are rounded up to the nearest whole number, and any decimal lower than 0.5 is rounded down to the nearest whole number). 4.2 Rounding Conventions for the Annual Secondary SO 2 (a) Hourly SO 2 (b) Daily mean values and the annual mean of those daily values are not rounded. (c) The annual secondary standard design value is calculated pursuant to section 5.2 of this appendix and then rounded to the nearest whole number or 1 ppb (decimals 0.5 and greater are rounded up to the nearest whole number, and any decimal lower than 0.5 is rounded down to the nearest whole number). 5. Calculation Procedures 5.1 Calculation Procedures for the 1-Hour Primary SO 2 (a) Procedure for identifying annual 99th percentile values. (i) The annual 99th percentile value for a year is the higher of the two values resulting from the following two procedures. (A) Procedure 1. (1) For the year, determine the number of days with at least 75 percent of the hourly values reported including State-flagged data affected by exceptional events which have been approved for exclusion by the Administrator. (2) For the year, from only the days with at least 75 percent of the hourly values reported, select from each day the maximum hourly value excluding State-flagged data affected by exceptional events which have been approved for exclusion by the Administrator. (3) Sort all these daily maximum hourly values from a particular site and year by descending value. (For example: (x[1], x[2], x[3], . . . x[n]). In this case, x[1] is the largest number and x[n] is the smallest value.) The 99th percentile is determined from this sorted series of daily values which is ordered from the highest to the lowest number. Using the left column of table 1, determine the appropriate range ( i.e., y 0.99, y (B) Procedure 2. (1) For the year, determine the number of days with at least one hourly value reported including State-flagged data affected by exceptional events which have been approved for exclusion by the Administrator. (2) For the year, from all the days with at least one hourly value reported, select from each day the maximum hourly value excluding State-flagged data affected by exceptional events which have been approved for exclusion by the Administrator. (3) Sort all these daily maximum values from a particular site and year by descending value. (For example: (x[1], x[2], x[3], . . . x[n]). In this case, x[1] is the largest number and x[n] is the smallest value.) The 99th percentile is determined from this sorted series of daily values which is ordered from the highest to the lowest number. Using the left column of table 1, determine the appropriate range ( i.e., y 0.99,y (b) The 1-hour primary standard design value for an ambient air quality monitoring site is mean of the three annual 99th percentile values, rounded according to the conventions in section 4.1 of this appendix. Table 1 Annual number of days with valid data for year “y” y P 0.99,y 1-100 1 101-200 2 201-300 3 301-366 4 5.2 Calculation Procedures for the Annual Secondary SO 2 (a) When the data for a site and year meet the data completeness requirements in section 3.2(b) of this appendix, or if the Administrator exercises the discretionary authority in section 3.2(c), the annual mean is simply the arithmetic average of all the daily mean values. (b) The annual secondary standard design value for an ambient air quality monitoring site is the mean of the annual means for three consecutive years, rounded according to the conventions in section 4.2 of this appendix. [89 FR 105785, Dec. 27, 2024] Appendix U to Part 50—Interpretation of the Primary and Secondary National Ambient Air Quality Standards for Ozone 1. General (a) This appendix explains the data handling conventions and computations necessary for determining whether the primary and secondary national ambient air quality standards (NAAQS) for ozone (O 3 3 3 3 (b) Whether to exclude or retain the data affected by exceptional events is determined by the requirements under §§ 50.1, 50.14 and 51.930. (c) The terms used in this appendix are defined as follows: 8-hour average 3 Annual fourth-highest daily maximum Collocated monitors 3 Daily maximum 8-hour average O 3 concentration Design value i.e., 3 Minimum data completeness requirements Monitor 3 O 3 monitoring season 3 Site 3 Site data record 3 Year 2. Selection of Data for use in Comparisons With the Primary and Secondary Ozone NAAQS (a) All valid hourly O 3 (b) All design value calculations shall be implemented on a site-level basis. If data are reported to EPA from collocated monitors, those data shall be combined into a single site data record as follows: (i) The monitoring agency shall designate one monitor as the primary monitor for the site. (ii) Hourly O 3 3 3 (c) In certain circumstances, including but not limited to site closures or relocations, data from two nearby sites may be combined into a single site data record for the purpose of calculating a valid design value. The appropriate Regional Administrator may approve such combinations after taking into consideration factors such as distance between sites, spatial and temporal patterns in air quality, local emissions and meteorology, jurisdictional boundaries, and terrain features. 3. Data Reporting and Data Handling Conventions (a) Hourly average O 3 (b) Moving 8-hour averages shall be computed from the hourly O 3 3 (c) The daily maximum 8-hour average O 3 i.e., 3 3 3 (d) A daily maximum 8-hour average O 3 3 3 (e) The primary and secondary O 3 3 3 3 4. Comparisons With the Primary and Secondary Ozone NAAQS (a) The primary and secondary national ambient air quality standards for O 3 3 i.e., (b) A design value greater than the level of the NAAQS is always considered to be valid. A design value less than or equal to the level of the NAAQS must meet minimum data completeness requirements in order to be considered valid. These requirements are met for a 3-year period at a site if valid daily maximum 8-hour average O 3 3 3 (c) When computing whether the minimum data completeness requirements have been met, meteorological or ambient data may be sufficient to demonstrate that meteorological conditions on missing days were not conducive to concentrations above the level of the NAAQS. Missing days assumed less than the level of the NAAQS are counted for the purpose of meeting the minimum data completeness requirements, subject to the approval of the appropriate Regional Administrator. (d) Comparisons with the primary and secondary O 3 Example 1—Site Meeting the Primary and Secondary O 3 Year Percent valid days within O 3 1st highest daily max 3 2nd highest daily max 3 3rd highest daily max 3 4th highest daily max 3 5th highest daily max 3 2014 100 0.082 0.080 0.075 0.069 0.068 2015 96 0.074 0.073 0.065 0.062 0.060 2016 98 0.070 0.069 0.067 0.066 0.060 Average 98 0.065 As shown in Example 1, this site meets the primary and secondary O 3 3 i.e., i.e., 3 Example 2—Site Failing to Meet the Primary and Secondary O3 O 3 Year Percent valid days within O 3 1st highest daily max 3 2nd highest daily max 3 3rd highest daily max 3 4th highest daily max 3 5th highest daily max 3 2014 96 0.085 0.080 0.079 0.074 0.072 2015 74 0.084 0.083 0.072 0.071 0.068 2016 98 0.083 0.081 0.081 0.075 0.074 Average 89 0.073 As shown in Example 2, this site fails to meet the primary and secondary O 3 3 i.e., i.e., [80 FR 65458, Oct. 26, 2015]

40 CFR Part 50 — National Primary and Secondary Ambient Air Quality Standards

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