EPA Equipment Leak Estimation & LDAR Compliance
EPA AR4: 25 • AR5: 28 • AR6: 29.8
Understand fugitive emission mechanisms, EPA estimation methods, LDAR program design, and regulatory compliance requirements
Fugitive emissions are unintentional leaks of gases (primarily methane and VOCs) from equipment components such as valves, flanges, pump seals, compressor seals, connectors, and open-ended lines. They differ from venting (intentional releases) and combustion emissions. EPA estimates fugitive emissions account for 5-15% of total facility GHG emissions in the midstream sector.
The EPA Average Emission Factor method multiplies the number of each component type by its published emission factor (in kg/hr per component) and the number of operating hours per year. Factors vary by component type (valve, pump, compressor seal, connector, etc.) and service (gas, light liquid, heavy liquid). This is the simplest EPA-approved method and requires no field measurements.
Leak Detection and Repair (LDAR) programs reduce fugitive emissions by identifying and fixing leaks on a regular schedule. EPA guidance credits are approximately: Monthly monitoring = 63% reduction, Quarterly monitoring = 52% reduction, Annual monitoring = 28% reduction. Programs using Optical Gas Imaging (OGI) cameras may achieve higher reductions than traditional EPA Method 21 sniffers.
Under the Clean Air Act, a facility is classified as a major source of Hazardous Air Pollutants (HAPs) if it emits 10 tons per year or more of any single HAP, or 25 tons per year or more of combined HAPs. Exceeding these thresholds triggers MACT (Maximum Achievable Control Technology) requirements and Title V permitting. For criteria pollutants, the Title V threshold is 100 TPY.