"Predictive emissions monitoring system" or "PEMS" means all of the equipment necessary to monitor process and control device operational parameters (for example, control device secondary voltages and electric currents) and other information (for example, gas flow rate, O₂ or CO₂ concentrations), and calculate and record the mass emissions rate (for example, pounds per hour) on a continuous basis.

(Source: Added at 49 Ill. Reg. 6237, effective April 23, 2025)