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Glossary:EPA method 21
EPA Method 21 is defined by the agency as being “a determination of volatile chemical compound leaks.” It is a method that is used by certified inspectors to best identify possible VOC leaks on process equipment sources. Depending on the nature of the operation, these equipment sources might include “valves, flanges, and other connections, pumps, and compressors, pressure relief devices, process drains, open-ended valves, pump and compressor seal system degassing vents, accumulator vessel vents, agitator seals, and access door seals.” Generally, this method is not meant to be used as a gauge for a measure of mass emission rate, but rather leak detection, specifically.
As stated in Section 6.0 of the EPA’s Method 21 document, suspected leaks must be tested with Method 21 by employing a specialized VOC monitoring instrument. Subsequently, samples must be collected, preserved, stored, and transported according to the guidelines.[1][2]
A specific emission detection methodology specified by the US EPA Technical Guidance on ‘Determination of Volatile Organic Compound Leaks’. This method is applicable for the determination of VOC leaks from process equipment. These sources include, but are not limited to, valves, flanges and other connections, pumps and compressors, pressure relief devices, process drains, open-ended valves, pump and compressor seal system degassing vents, accumulator vessel vents, agitator seals and access door seals.[3]