Ill. Admin. Code tit. 35, § 217.184
Except as provided for under Section 217.152, on or after January 1, 2015, no person shall cause or allow emissions of NOx into the atmosphere from any process heater 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 and Rated Heat Input Capacity (mmBtu/hr) | NOx Emissions Limitation (lb/mmBtu) or Requirement Before July 1, 2025 |
| Natural Gas or Other Gaseous Fuels | Process heater greater than 100 | 0.08 |
| Process heater less than or equal to 100 | Combustion tuning | |
| Residual Fuel Oil | Process heater greater than 100, natural draft | 0.10 |
| Process heater greater than 100, mechanical draft | 0.15 | |
| Process heater less than or equal to 100 | Combustion tuning | |
| Other Liquid Fuels | Process heater greater than 100, natural draft | 0.05 |
| Process heater greater than 100, mechanical draft | 0.08 | |
| Process heater less than or equal to 100 | Combustion tuning |
| Fuel | Emission Unit Type and Rated Heat Input Capacity (mmBtu/hr) | NOx Emissions Limitation (lb/mmBtu) or Requirement On and after July 1, 2025 |
| Natural Gas or Other Gaseous Fuels | Process heater greater than 50 | 0.08 |
| Process heater less than or equal to 50 | Combustion tuning | |
| Residual Fuel Oil | Process heater greater than 50, natural draft | 0.10 |
| Process heater greater than 50, mechanical draft | 0.15 | |
| Process heater less than or equal to 50 | Combustion tuning | |
| Other Liquid Fuels | Process heater greater than 50, natural draft | 0.05 |
| Process heater greater than 50, mechanical draft | 0.08 | |
| Process heater less than or equal to 50 | Combustion tuning |
(Source: Amended at 49 Ill. Reg. 6355, effective April 23, 2025)