40 C.F.R. § 52.2621
Classification of regions.
Cite as 40 C.F.R. § 52.2621 (2026)
The Wyoming plan was evaluated on the basis of the following classifications: Air quality control region Pollutant Particulate matter Sulfur oxides Nitrogen dioxide Carbon monoxide Photochemical oxidants (hydrocarbons) Cheyenne Intrastate II III III III III Casper Intrastate II III III III III Wyoming Intrastate III III III III III [37 FR 10904, May 31, 1972]