75-2-203. Department to set emission levels. (1) Subject to subsection (2), the department may establish the limitations of the levels, concentrations, or quantities of emissions of various pollutants from any source necessary to prevent, abate, or control air pollution. Except as otherwise provided in or pursuant to this section, those levels, concentrations, or quantities are controlling, and no emission in excess of those levels is lawful.

(2) (a) Except as provided in subsection (2)(b), the department may not fix more stringent requirements governing the emission of air pollutants than the federal standards or limitations established in the federal Clean Air Act for the emission of regulated pollutants.

(b) Subsection (2)(a) does not apply to requirements:

(i) governing the emissions of air pollutants established prior to May 1, 2025; and

(ii) necessary in areas classified as nonattainment, maintenance, or to prevent nonattainment, as approved by the department, to comply with national ambient air quality standards as required in the federal Clean Air Act.

(3) The department may by rule use any widely recognized measuring system for measuring emission of air contaminants.