Q548. For Acid Gas Removal (AGR) vents is the use of a meter to measure flow rates required?

A548.The rule requires the use of a meter if one is in place.  If a continuous vent flow meter is not already in place, then reporters have the choice of installing a continuous vent flow meter or alternatively using Calculation Methods 3 or 4 in 40 CFR 98.233(3) or (4), respectively, to calculate emissions

Beginning with Reporting Year 2024, reporters may elect to use Calculation Method 4 rather than Calculation Method 2 if a CEMS is not available but a vent meter is installed. In cases where a vent stream has high concentrations of H₂S, there could be safety concerns with collecting the quarterly samples needed to determine the vent gas composition under Calculation Method 2, and this provision provides an alternative method. Reporters that elect to use Calculation Method 4 must determine the difference between the annual volume of vent gas measured by the vent meter and the simulated annual volume of vent gas according to 40 CFR 98.233(d)(12) (40 CFR 98.233(d)(9) beginning on January 1, 2025). If the simulations conducted under Calculation Method 4 do not agree with the measured annual volume of vent gas, then that could be an indication that the simulation results may not be an accurate representation of the emissions. Therefore, if the calculated percent difference in vent gas volumes is greater than 20 percent, 40 CFR 98.236(d)(2)(iii)(M)(3) (40 CFR 98.236(d)(2)(iii)(O)(3) beginning on January 1, 2025) requires reporters to provide a brief description of the reason for the difference..