Ill. Admin. Code tit. 35, § 217.224
a) On and after January 1, 2015, no person shall cause or allow emissions of NOx into the atmosphere from any cement kiln 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.
| Emission Unit Type | NOx Emissions Limitation (lb/ton clinker produced) Before July 1, 2025 |
| Long dry kiln | 5.1 |
| Short dry kiln | 5.1 |
| Preheater kiln | 3.8 |
| Preheater/precalciner kiln | 2.8 |
| Emission Unit Type | NOx Emissions Limitation (lb/ton clinker produced) On and after July 1, 2025 |
| Long dry kiln | 3.0 |
| Short dry kiln | 2.3 |
| Preheater kiln | 3.8 |
| Preheater/precalciner kiln | 2.8 |
b) On and after January 1, 2015, no person shall cause or allow emissions of NOx into the atmosphere from any lime kiln 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/ton lime produced) |
| Gas | Rotary kiln | 2.2 |
| Coal | Rotary kiln | 2.5 |
(Source: Amended at 49 Ill. Reg. 6355, effective April 23, 2025)