The number on the flare
A flare's job is destruction: at 95 percent destruction efficiency, 95 percent of the hydrocarbon mass entering the flame is destroyed. EPA's 2020 flare efficiency study, which underpins the agency's emissions factors, measured air- and steam-assisted flares and recorded combustion efficiency above 98 percent under well-operated conditions. The same study found efficiency falls when steam rates run high or the vent gas flow drops below the flare's design range, which is why the operating envelope matters as much as the tip design.
The rules moved the number into the permit
NSPS OOOOb, the 2024 methane rule for new sources, requires that associated gas be routed to a sales line or a useful purpose, and where that is demonstrated infeasible, it allows routing to a flare or control device that achieves at least 95 percent reduction in methane and VOC emissions. The rule adds continuous monitoring of vent gas net heating value and combustion zone conditions, and EPA's April 2026 amendments adjusted the net heating value monitoring requirements and the alternative performance test option. The number in your state permit is the one that governs.
What operators measure
Compliance evidence is continuous, not a one-day test: vent gas flow, gas composition or net heating value, assist gas rates, and flame presence. The 2026 amendments expanded the streams exempt from monitoring due to high heating value and refined the alternative test options, but the direction is the same: an operator must be able to show the flare was within its operating window whenever gas flowed. The monitoring record, not the flare's reputation, is what a regulator reviews.
Flare performance connects to the other measured numbers on a lease: well test data, H2S monitoring, and methane detection. If the monitoring data exists only in the vendor's report and nobody reconciles it to the operations log, an operations audit will show where the compliance record and the field reality stopped agreeing.