Volatile Oraganics Compounds Emissions in Captured Stream – USEPA Method 204C

USEPA Method 204C is used for the determination of volatile organic compounds (VOC) content of captured gas streams.  It is used in the development of a gas/gas protocol in which uncaptured emissions are also measured for determining VOC capture efficiency (CE) for surface coating and printing operations.  A dilution system is used to reduce the VOC concentration of the captured emissions to about the same concentration as the uncaptured emissions.
 
A gas sample is extracted from the source using an in-stack dilution probe through a heated sample line and, if necessary, a glass fiber filter to a flame ionization analyzer (FIA).  The sample train contains a sample gas manifold which allows multiple points to be sampled using a single FIA.
 
A CE test consists of at least three sampling runs.  Each run covers at least one complete production cycle, but is at least 3 hours long.  The sampling time for each run need not exceed 8 hours, even if the production cycle is not completed.  Alternative sampling times are used with the approval of the Administrator.
 
The amount of VOC captured (G) is calculated as the sum of the products of the VOC content (CGj), the flow rate (QGj), and the sampling time (ÉΔC) from each captured emissions point.
 
The procedure is not acceptable in certain site-specific situations:

• if direct-fired heaters or other circumstances affect the quantity of VOC at the control device inlet;
• if particulate organic aerosols are formed in the process and are present in the captured emissions.