Continuous Emission Monitoring in the United States

Continuous Emission Monitoring (CEM) in Environmental Law

A method of continuous testing for air emissions. The Clean Air Act Amendments of 1990 order this type of monitoring for sources that emit acid rain pollutants (sulfur dioxide and nitrogen oxides). Continuous emission monitoring may also be required by a state when it issues permits for other types of air pollution sources to operate within its borders. Though the new CEM requirement adds considerable cost to air pollution control, it enables the discharger to quickly spot problems in a process or control equipment so they can be fixed before significant amounts of pollution escape.

Information obtained from continuous emission monitoring must be supplied to the EPA or state as specified by regulations. If a source cannot provide data to prove it is complying with the law, the EPA can assume it was operating in an uncontrolled manner during that time period.
Based on “Environment and the Law. A Dictionary”.