Code of Federal Regulations > Title 40 > Chapter I > Part 53 > Subpart F > Appendix - Table F-3 to Subpart F of Part 53—Critical Parameters of Idealized Ambient Particle Size Distributions

Regulations last checked for updates: Feb 22, 2025

Title 40 - Protection of Environment last revised: Nov 22, 2025

Appendix - Table F-3 to Subpart F of Part 53—Critical Parameters of Idealized Ambient Particle Size Distributions

Idealized Distribution	Fine Particle Mode			Coarse Particle Mode			PM 2.5/PM 10 Ratio	FRM Sampler Expected Mass Conc. (µg/m ³)
Idealized Distribution	MMD (µm)	Geo. Std. Dev.	Conc. (µg/m ³)	MMD (µm)	Geo. Std. Dev.	Conc. (µg/m ³)	PM 2.5/PM 10 Ratio	FRM Sampler Expected Mass Conc. (µg/m ³)
Coarse	0.50	2	12.0	10	2	88.0	0.27	13.814
“Typical”	0.50	2	33.3	10	2	66.7	0.55	34.284
Fine	0.85	2	85.0	15	2	15.0	0.94	78.539

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.