Ill. Admin. Code tit. 35, § 204.520 – Minor Source Baseline Date

a) "Minor source baseline date" means the earliest date after the trigger date on which a major stationary source or a major modification subject to 40 CFR 52.21 or this Part submits a complete application under the relevant regulations. The trigger date is:
1. 1) In the case of PM₁₀ and SO₂, August 7, 1977;
2. 2) In the case of NO₂, February 8, 1988; and
3. 3) In the case of PM_2.5, October 20, 2011.
b) The baseline date is established for each pollutant for which increments or other equivalent measures have been established if:
1. 1) The area in which the proposed source or modification would construct is designated as attainment or unclassifiable under section 107(d)(1)(A)(ii) or (iii) of the CAA (42 USC 7407(d)(1)(A)(ii) or (iii)) for the pollutant on the date of its complete application under 40 CFR 52.21 or this Part; and
2. 2) In the case of a major stationary source, the pollutant would be emitted in significant amounts or, in the case of a major modification, there would be a significant net emissions increase of the pollutant.
c) Any minor source baseline date established originally for the TSP increments shall remain in effect and shall apply for purposes of determining the amount of available PM₁₀ increments, except that the Agency shall rescind a minor source baseline date when it can be shown, to the satisfaction of the Agency, that the emissions increase from the major stationary source, or net emissions increase from the major modification, responsible for triggering that date did not result in a significant amount of PM₁₀ emissions.