1. (1) In areas designated as Class I, II, or III, increases in pollutant concentration over the baseline concentration shall be limited to the following:

2. (2) For any period other than an annual period, the applicable maximum allowable increase may be exceeded during one such period per year at any one location.

   Pollutant

   Maximum allowable increase (micrograms per cubic meter)

   CLASS I

   Particulate matter:
   PM-2.5, annual arithmetic mean.................................................................................1
   PM-2.5, 24-hr maximum..............................................................................................2
   PM-10, annual arithmetic mean..................................................................................4
   PM-10, 24-hr maximum...............................................................................................8
   Sulfur dioxide (SO 2 ):
   Annual arithmetic mean...............................................................................................2
   24-hr maximum.............................................................................................................5
   3-hr maximum.............................................................................................................25
   Nitrogen dioxide (NO 2 ):
   Annual arithmetic mean...............................................................................................2.5

   CLASS II

   Particulate matter:
   PM-2.5, annual arithmetic mean.................................................................................4
   PM-2.5, 24-hr maximum..............................................................................................9
   PM-10, annual arithmetic mean................................................................................17
   PM-10, 24-hr maximum.............................................................................................30
   Sulfur dioxide (SO 2 ):
   Annual arithmetic mean.............................................................................................20
   24-hr maximum...........................................................................................................91
   3-hr maximum...........................................................................................................512
   Nitrogen dioxide (NO 2 ):
   Annual arithmetic mean.............................................................................................25

   CLASS III

   Particulate matter:
   PM-2.5, annual arithmetic mean.................................................................................8
   PM-2.5, 24-hr maximum............................................................................................18
   PM-10, annual arithmetic mean................................................................................34
   PM-10, 24-hr maximum.............................................................................................60
   Sulfur dioxide (SO 2 ):
   Annual arithmetic mean.............................................................................................40
   24-hr maximum.........................................................................................................182
   3-hr maximum............................................................................................................700
   Nitrogen dioxide (NO 2 ):
   Annual arithmetic mean..............................................................................................50

Authorizing statute(s): 75-2-111, 75-2-203, MCA

Implementing statute(s): 75-2-202, 75-2-203, 75-2-204, MCA

History: NEW, 1993 MAR p. 2919, Eff. 12/10/93; AMD, 1994 MAR p. 2829, Eff. 10/28/94; TRANS, from DHES, 1996 MAR p. 2285; AMD, 2011 MAR p. 2134, Eff. 10/14/11.