Stationary source sampling is conducted to evaluate gas stream emissions to the atmosphere from stacks, ducts or process exhausts. A pollutant’s concentration is measured by extracting a known volume from the gas stream and determining the average stack gas flow rate over the sampling period. The mass emission rate of each constituent then may be calculated. In the area of Stack Sampling Methods, there are 3 major categories of testing: Isokinetic Reference Methods, Instrumental Reference Methods (IRM), and Gaseous Sampling (which includes sampling for mercury).

The Apex isokinetic method 5 sampling system offers modular components that can be arranged and re-arranged to perform multiple U.S. EPA Reference Methods. Select from manual, digital or automated meter consoles, as well as a wide range of heated filter and impinger boxes, heavy-wall glassware with unground o-ring ball joints, probes built to customer specified lengths, new designs for umbilical cords, and custom modifications to meet your unique needs. All delivered in a timely manner at a competitive price.

Obtaining a representative sample of particulate matter from a gas stream requires a more complex procedure than sampling only for gases. Particles can be either liquid droplets or solids. Representative sampling requires that the velocity of the gas/particle mixture passing into the sampling nozzle must be as close as possible to the velocity of the gas stream in the stack or duct. When the velocities are the same, the sampling is isokinetic. During the entire sampling period, the stack velocity must be monitored constantly and the pumping rate adjusted so that the nozzle intake velocity matches as closely as possible the velocity of the in-stack gas/particle mixture. In addition, the pumping rate needs to be adjusted for differences in pressure, temperature and moisture between the stack conditions and the pump or meter console. The exact steps to conduct this type of sampling are spelled out in U.S. EPA Reference Method 5. This method also requires knowledge of U.S. EPA References Methods 1 through 4.