Continuous Emission Monitoring System (CEMS) is the total equipment necessary for the determination of a gas or particulate matter concentration or emission rate using pollutant analyzer measurements and a conversion equation, graph, or computer program to produce results in units of the applicable emission limitation or standard.
CEMS are required under some of the EPA regulations for either continual compliance determinations or determination of exceedances of the standards. The individual subparts of the EPA rules specify the reference methods that are used to substantiate the accuracy and precision of the CEMS.
Performance Speciﬁcations are used for evaluating the acceptability of the CEMS at the time of or soon after installation and whenever speciﬁed in the regulations. Continuous Emission Monitoring System measures high concentrations of gas at the point of emission, namely from a chimney or stack. These gases may include SO2 , NOx, CO, H2S and NH3 , monitored using specially designed gas analyzers.