Code of Federal Regulations > Title 40 > Chapter I > Part 53 > Subpart A > Appendix - Table A-1 to Subpart A of Part 53—Summary of Applicable Requirements for Reference and Equivalent Methods for Air Monitoring of Criteria Pollutants

Regulations last checked for updates: Feb 03, 2026

Title 40 - Protection of Environment last revised: Dec 31, 2026

Appendix - Table A-1 to Subpart A of Part 53—Summary of Applicable Requirements for Reference and Equivalent Methods for Air Monitoring of Criteria Pollutants

Pollutant	Reference or equivalent	Manual or automated	Applicable appendix of part 50 of this chapter	Applicable subparts of this part
Pollutant	Reference or equivalent	Manual or automated	Applicable appendix of part 50 of this chapter	A	B	C	D	E	F
SO2	Reference	Manual	A-2
		Automated	A-1	✓	✓
	Equivalent	Manual	A-1	✓		✓
		Automated	A-1	✓	✓	✓
CO	Reference	Automated	C	✓	✓
	Equivalent	Manual	C	✓		✓
		Automated	C	✓	✓	✓
O3	Reference	Automated	D	✓	✓
	Equivalent	Manual	D	✓		✓
		Automated	D	✓	✓	✓
NO2	Reference	Automated	F	✓	✓
	Equivalent	Manual	F	✓		✓
		Automated	F	✓	✓	✓
Pb	Reference	Manual	G
	Equivalent	Manual	G	✓		✓
		Automated	G	✓		✓
PM10-Pb	Reference	Manual	Q
	Equivalent	Manual	Q	✓		✓
		Automated	Q	✓		✓
PM10	Reference	Manual	J	✓			✓
	Equivalent	Manual	J	✓		✓	✓
		Automated	J	✓		✓	✓
PM2.5	Reference	Manual	L	✓				✓
	Equivalent Class I	Manual	L	✓		✓		✓
	Equivalent Class II	Manual	L ¹	✓		² ✓		✓	1 2 ✓
	Equivalent Class III	Automated	L ¹	✓		✓		✓	¹ ✓
PM10-2.5	Reference	Manual	L, ² O	✓				✓
	Equivalent Class I	Manual	L, ² O	✓		✓		✓
	Equivalent Class II	Manual	L, ² O	✓		² ✓		✓	^1,2 ✓
	Equivalent Class III	Automated	¹ L, 1 2 O	✓		✓		✓	¹ ✓

¹ Some requirements may apply, based on the nature of each particular candidate method, as determined by the Administrator.

² Alternative Class III requirements may be substituted.

[89 FR 16382, 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.