17.8.804 : AMBIENT AIR INCREMENTS - Administrative Rules of the State of Montana

17.8.804 AMBIENT AIR INCREMENTS

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

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 (SO₂):
           Annual arithmetic mean...............................................................................................2
           24-hr maximum.............................................................................................................5
           3-hr maximum.............................................................................................................25
Nitrogen dioxide (NO₂):
           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 (SO₂):
           Annual arithmetic mean.............................................................................................20
           24-hr maximum...........................................................................................................91
           3-hr maximum...........................................................................................................512
Nitrogen dioxide (NO₂):
           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 (SO₂):
           Annual arithmetic mean.............................................................................................40
           24-hr maximum.........................................................................................................182
           3-hr maximum............................................................................................................700
Nitrogen dioxide (NO₂):
           Annual arithmetic mean..............................................................................................50

(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.

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; 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.