40 C.F.R. § 51.901
Applicability of part 51
The provisions in subparts A through W of part 51 apply to areas for purposes of the 8-hour NAAQS to the extent they are not inconsistent with the provisions of this subpart.
The provisions in subparts A through W of part 51 apply to areas for purposes of the 8-hour NAAQS to the extent they are not inconsistent with the provisions of this subpart.