"Significant emissions unit" means an emissions unit that emits or has the potential to emit a PAL pollutant in an amount that is equal to or greater than the applicable significant level (as defined in Section 203.1370 or in the CAA, whichever is lower) for that PAL pollutant, but less than the amount that would qualify the unit as a major emissions unit as defined in Section 203.2190.

(Source: Added at 49 Ill. Reg. 6237, effective April 23, 2025)