ABSTRACT
Environmental Protection Agency (EPA) Method 5, "Determination of Particulate Emissions from Stationary Sources" has a number of unique requirements designed to ensure that a representative sample is extracted from the duct or stack. One of the most significant of these is the requirement for isokinetic sampling. The chapter discusses how to set the sampling rate to isokinetic. It is clear that the sampling nozzle velocity must remain equal to the duct or stack gas velocity at all times, in order to ensure that the sample of gas removed is representative. Since the nozzle area has a great effect on the sampling velocity, the selection of nozzle diameter is a significant decision in the process of isokinetic sampling. The gas velocity may change when the probe is moved, or may vary with time; thus, real-time nozzle and stack gas velocity measurements must be available to allow the emission tester to make adjustments in the sample flow rate.
