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Air Emission Measurement Center (EMC)

EMC: Continuous Emission Monitoring Systems

Information and Guidelines

A 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.

Quality assurance procedures in Appendix F to 40 CFR 60 are used to evaluate the effectiveness of quality control (QC) and quality assurance (QA) procedures and the quality of data produced by any CEMS that is used for determining compliance with the emission standards on a continuous basis as specified in the applicable regulation.

A predictive emission monitoring system (PEMS) is the total equipment necessary for the determination of a gas concentration or emission rate using process or control device operating parameter measurements and a conversion equation, a graph, or computer program to produce results in units of the applicable emission limitation or standard. The EPA is studying the applicability of PEMS for NOx compliance determinations for various sources. A draft protocol for assessing the accuracy and precision of PEMS has been developed and is expected to be proposed sometime in the near future.

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