"Heat input" means the product of the gross heating value of the fuel and the amount of fuel combusted in a combustion device. Heat input does not include the heat derived from preheated combustion air, recirculated flue gases, or exhaust from other sources.
Ill. Admin. Code tit. 35, § 211.2815
Added at 25 Ill. Reg. 108, effective December 26, 2000