Oxygen trim system
Oxygen trim system means a system of monitors that is used to maintain excess air at the desired level in a combustion device over its operating range. A typical system consists of a flue gas oxygen and/or carbon monoxide monitor that automatically provides a feedback signal to the combustion air controller or draft controller.
40 CFR § 60.2875
Terms used but not defined in this subpart are defined in the Clean Air Act and subparts A and B of this part.