Smoke School Information in Illinois

Illinois Acceptance Status for VirtualOpacity^® — EPA ALT-152A

Pending Acceptance.

Illinois Visible Emissions / Opacity Standard

The opacity limit for Illinois is Sec. 212.122(a): 20% for fuel-combustion units >250 MMBtu/hr constructed/modified on/after April 14, 1972 (exception to 40% for 3 min/hr per (b)); Sec. 212.123(a): 30% all other emission units (exception to 60% for 8 min/hr, <=3x/24 hr per (b)), as established under 35 Ill. Adm. Code 212.122(a)-(b) and 212.123(a)-(b).

Compliance is demonstrated via EPA Method 9 (40 CFR Part 60, Appendix A, incorporated by reference in § 212.113).

Averaging period: 6-minute average; exception: § 212.122 allows >20% but ≤40% aggregating 3 min/hr; § 212.123 allows >30% but ≤60% aggregating 8 min/hr (each limited to 3 times per 24 hr)

Illinois has a tiered visible emissions standard: 20% for large boilers/fuel combustion, but 30% for all other emission units — one of the higher general standards nationally. Adjusted opacity standards available via § 212.126 if source demonstrates PM compliance at test time.

Last verified July 8, 2026

Note: Regulations change — always verify current requirements with your state's air quality agency before making compliance decisions. This page is for informational purposes and is not legal advice; consult a qualified attorney or environmental compliance professional for guidance specific to your facility.