What is stationary source emissions monitoring?

Through the Clean Air Act, the United States Environmental Protection Agency (EPA) is responsible for regulating the emissions of pollutants from stationary sources (CAA). The purpose of stationary source testing, also known as stack testing or source emissions testing, is to assist operators in better understanding the composition of their emissions and to ensure that control systems are functioning as intended. The results of the testing demonstrate that emissions are within the permissible levels.

Some monitoring devices directly measure the pollutant of concern coming from a stationary source, while others measure a surrogate for the pollutant of concern. Here are some measurement techniques that monitoring devices may use, including Continuous Emission Monitoring Systems (CEMS), Continuous Opacity Monitoring Systems (COMS), and Continuous Parametric Monitoring systems (CPMS). Nitrogen Oxides (NOx) Continuous Emissions Monitoring Systems (CEMS) are an example of a monitoring device that directly measures the pollutant of concern. These CEMS are used to monitor the NOx concentration (emissions level) of the effluent that is discharged from a process stack on a stationary source that is required to comply with a NOx emissions limit. The Continuous Emissions Monitoring System (CEMS) for Carbon Monoxide (CO) is an example of a monitoring device that measures a surrogate pollutant. Its purpose is to monitor the CO concentration of the effluent from a stationary combustion source that needs to comply with a limit for volatile organic compounds (VOC). Because CO is a byproduct of incomplete combustion and increased levels of CO signal that incomplete combustion has occurred, the concentration of CO is being utilized in this instance as a stand-in for the concentration of VOCs. Devices such as thermocouples and pressure transducers are examples of parametric monitoring equipment. These two types of devices monitor temperature and pressure, respectively.