(1) Any new major stationary source or major modification which would locate anywhere in an area designated as nonattainment for a national ambient air quality standard under 40 CFR 81.327 and which is major for the pollutant for which the area is designated nonattainment, shall, prior to construction, obtain from the department a Montana air quality permit in accordance with subchapter 7 and all requirements contained in this subchapter if applicable. A major stationary source or major modification exempted from the requirements of subchapter 7 under ARM 17.8.744 and 17.8.745 which would locate anywhere in an area designated as nonattainment for a national ambient air quality standard under 40 CFR 81.327 and which is major for the pollutant for which the area is designated nonattainment, shall, prior to construction, still be required to obtain a Montana air quality permit and comply with the requirements of ARM 17.8.748, 17.8.749, 17.8.756, 17.8.759, and 17.8.760 and with all applicable requirements of this subchapter.

(2) Any source or modification located anywhere in an area designated as nonattainment for a national ambient air quality standard under 40 CFR 81.327 which becomes a major stationary source or major modification for the pollutant for which the area is designated nonattainment solely by virtue of a relaxation in any enforceable limitation which was established after August 7, 1980, on the capacity of the source or modification otherwise to emit a pollutant (such as a restriction on hours of operation) shall obtain from the department a Montana air quality permit as though construction had not yet commenced on the source or modification, in accordance with subchapter 7 and all requirements of this subchapter.

(3) Sulfur dioxide (SO₂) is a precursor to PM-2.5 in a PM-2.5 nonattainment area.

(4) Nitrogen oxides are presumed to be precursors to PM-2.5 in a PM-2.5 nonattainment area, unless the applicant demonstrates that emissions of nitrogen oxides from sources in the PM-2.5 nonattainment area are not a significant contributor to that area's ambient PM-2.5 concentrations.

(5) Volatile organic compounds and ammonia are presumed not to be precursors to PM-2.5 in a PM-2.5 nonattainment area unless emissions of volatile organic compounds or ammonia from sources in the area are a significant contributor to that area's ambient PM-2.5 concentrations.

(6) PM-2.5 emissions and PM-10 emissions shall include gaseous emissions from a source or activity that condense to form particulate matter at ambient temperatures.

(7) Applicability determinations made prior to January 1, 2011, without accounting for condensable particulate matter, are not subject to (5).