Q767. What are the requirements for determining the volume of gas sent to a flare?

A767. The requirements for Reporting Year (RY) 2025 are specified in 40 CFR 98.233(n)(3) of the May 14, 2024, amended rule, and requirements for prior years are set forth at 40 CFR 98.233(n)(1) of the rule as it existed prior to the amendments. 

For all years, if you have a continuous flow measurement device on the flare, you must use the measured flow volumes to calculate the flare gas emissions. The amendments also specify that if you indirectly measure flow using continuous parameter monitoring systems combined with engineering calculations for RY 2025 or later, you must use the measured volume to calculate emissions.

For years prior to RY 2025, if all of the flare gas is not measured by the existing flow measurement device, then the flow that is not measured can be estimated using engineering calculations based on best available data or company records.  If you do not have a continuous flow measurement device on the flare, you can install a flow measuring device on the flare or use engineering calculations based on process knowledge, company records, and best available data.

For RY 2025, the amendments specify that if flow is not measured continuously (either the total flow at the inlet to the flare or the individual flows from each source that is routed to the flare), then flows from the individual sources must be determined using either the same calculations that are specified by the rule for determining vented emissions from specified source types or engineering calculations based on process knowledge, company records, and best available data for other source types.