The purpose of Method 30B sorbent traps is to measure total vapor phase mercury (Hg) emissions from coal fired sources. Knowledge of Methods 1, 4, and 5 is recommended. The testing should be done after the stack gas has passed through all pollution control devices, i.e. with a stream that is low in particulates. Method 30B is used to test the accuracy of current vapor phase Hg constant emissions monitoring systems (CEMS) and can also be used to test for the compliance of mercury emissions standards. The method requires a minimum of two simultaneous sampling trains. For more information on this method, please visit Clean Air's EPA directory for test methods.