(1) No concentration of a pollutant shall exceed the concentration permitted under either the applicable secondary or primary national ambient air quality standard, whichever concentration is lowest for the pollutant for a period of exposure.

History: 75-2-111, 75-2-203, MCA; IMP, 75-2-202, 75-2-203, 75-2-204, MCA; NEW, 1993 MAR p. 2919, Eff. 12/10/93; TRANS, from DHES, 1996 MAR p. 2285.