40 C.F.R. § 81.16
The Metropolitan Denver Intrastate Air Quality Control Region (Colorado) consists of the territorial area encompassed by the boundaries of the following jurisdictions or described area (including the territorial area of all municipalities (as defined in section 302(f) of the Clean Air Act, 42 U.S.C. 1857h(f) ) geographically located within the outermost boundaries of the area so delimited):
In the State of Colorado: Adams County, Arapahoe County, Boulder County, Clear Creek County, Denver County, Douglas County, Gilpin County, Jefferson County.
(Sec. 301(a), 81 Stat. 490, 504; 42 U.S.C. 1857g(a) , as amended by sec. 15(c)(2) of Pub. L. 91-604 )
40 C.F.R. §81.16
For purposes of identification, the Regions are referred to by Colorado authorities as follows: Sec.
481.172 Comanche Intrastate Air Quality Control Region: Region Three.
481.173 Grand Mesa Intrastate Air Quality Control Region: Region Seven.
481.174 Pawnee Intrastate Air Quality Control Region: Region One.
481.175 San Isabel Intrastate Air Quality Control Region: Region Four.
481.176 San Luis Intrastate Air Quality Control Region: Region Five.
481.177 Yampa Intrastate Air Quality Control Region: Region Eight.
481.16 Metropolitan Denver Intrastate Air Quality Control Region: Region Two.