Regulations last checked for updates: Jan 18, 2025

Title 40 - Protection of Environment last revised: Dec 30, 2025
All TitlesTitle 40Chapter IPart 53Subpart CAppendix - Table C-4 to Subpart C of Part 53—Test Specifications for PM 10, PM 2.5 and PM 10-2.5 Candidate Equivalent Methods
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Appendix - Table C-4 to Subpart C of Part 53—Test Specifications for PM 10, PM 2.5 and PM 10-2.5 Candidate Equivalent Methods

Table C-4 to Subpart C of Part 53—Test Specifications for PM10, PM2.5, and PM10-2.5 Candidate Equivalent Methods

Specification PM10 PM2.5 PM10-2.5
Class I Class II Class III Class II Class III
Acceptable concentration range (Rj), µg/m 35-3003-2003-2003-2003-2003-200.
Minimum number of test sites212424.
Minimum number of candidate method samplers or analyzers per site333 13 13 13. 1
Number of reference method samplers per site333 13 13 13. 1
Minimum number of acceptable sample sets per site for PM10 methods:
Rj < 20 µg/m 33
Rj > 20 µg/m 33
Total10
Minimum number of acceptable sample sets per site for PM2.5 and PM10-2.5 candidate equivalent methods:
Rj < 15 µg/m 3 for 24-hr or Rj < 8 µg/m 3 for 48-hr samples.33333.
Rj > 15 µg/m 3 for 24-hr or Rj > 8 µg/m 3 for 48-hr samples33333.
Each season1023232323.
Total, each site102323 (46 for two-season sites)2323 (46 for two-season sites).
Precision of replicate reference method measurements, PRj or RPRj, respectively; RP for Class II or III PM2.5 or PM10-2.5, maximum5 µg/m 3 or 7%.2 µg/m 3 or 5%.10% 210% 210% 210%. 2
Precision of PM2.5 or PM10-2.5 candidate method, CP, each site10% 215% 215% 215%. 2
Slope of regression relationship1 ±0.101 ±0.051 ±0.101 ±0.101 ±0.101 ±0.12.
Intercept of regression relationship, µg/m 30 ±50 ±1Between: 13.55—(15.05 × slope), but not less than—1.5; and 16.56—(15.05 × slope), but not more than +1.5Between: 15.05—(17.32 × slope), but not less than—2.0; and 15.05—(13.20 × slope), but not more than +2.0Between: 62.05—(70.5 × slope), but not less than—3.5; and 78.95—(70.5 × slope), but not more than +3.5Between: 70.50—(82.93 × slope), but not less than—7.0; and 70.50—(61.16 × slope), but not more than +7.0.
Correlation of reference method and candidate method measurements≥ 0.97≥ 0.97≥ 0.93—for CCV ≤ 0.4;
≥ 0.85 + 0.2 × CCV—for 0.4 ≤ CCV ≤ 0.5;
≥ 0.95—for CCV ≥ 0.5

1 Some missing daily measurement values may be permitted; see test procedure.

2 Calculated as the root mean square over all measurement sets.

[89 FR 16386, Mar. 6, 2024]
authority: Sec. 301(a) of the Clean Air Act (42 U.S.C. sec. 1857g(a)), as amended by sec. 15(c)(2) of Pub. L. 91-604, 84 Stat. 1713, unless otherwise noted
source: 40 FR 7049, Feb. 18, 1975, unless otherwise noted.
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