Ill. Admin. Code tit. 35, § 217.344
On and after January 1, 2015, no person shall cause or allow emissions of NOx into the atmosphere from any fossil fuel-fired stationary boiler to exceed the following limitations. Until July 1, 2025, compliance must be demonstrated with the applicable emissions limitation on an ozone season and annual basis. On and after July 1, 2025, compliance must be demonstrated with the applicable emissions limitation on a 30-day rolling average basis.
| Fuel | Emission Unit Type | NOx Emissions Limitation (lb/mmBtu) |
| Solid | Boiler | 0.12 |
| Natural gas | Boiler | 0.06 |
| Liquid | Boiler that commenced operation before January 1, 2008 | 0.10 |
| Boiler that commenced operation on or after January 1, 2008 | 0.08 |
(Source: Amended at 49 Ill. Reg. 6355, effective April 23, 2025)