Continuous Emissions Monitoring Systems (CEMS)



The North Carolina Division of Air Quality (DAQ) may require certain facilities or source categories to install, operate, and maintain a continuous emissions monitoring system (CEMS) or continuous opacity monitoring system (COMS) in order to demonstrate compliance with a specific air pollution regulation or permit condition. By continuously monitoring pollutants emitted by a facility, regulatory agencies can be assured the facility is being properly operated and the environment is adequately protected. Emission sources are required to be self-reporting when permit limits are exceeded. CEMS may serve many purposes including:

  • Indicators of control equipment performance
  • Compliance monitoring of permitted limits
  • Accurate measurement for emissions trading programs
  • Emissions inventories

Each permitted CEMS is required by DAQ to be certified in accordance with performance specifications established by the Environmental Protection Agency (EPA). The certification process ensures the CEMS is properly located, measures emissions accurately and operates reliably. Many of the rules governing compliance with CEMS and COMS can be found in Title 40, Part 60 of the Code of Federal Regulations (40 CFR 60).


Both federal and state air quality regulations may require continuous emissions monitoring systems. For example, a facility can be required to monitor according to provisions found in:

  • Subchapter 2D of the North Carolina Air Quality Rules
  • A specific permit condition
  • The State Implementation Plan (SIP) for North Carolina in 40 CFR Part 51
  • New Source Performance Standards (NSPS) in 40 CFR Part 60
  • National Emission Standards for Hazardous Air Pollutants (NESHAP) in 40 CFR Part 61
  • Maximum Achievable Control Technology (MACT) standards 40 CFR Part 63
  • Prevention of Significant Deterioration (PSD) in 40 CFR Part 52 and Part D of the Clean Air Act
  • Acid Rain regulations in 40 CFR Part 75
  • Title V (Renewable Operating Permit) Periodic and Compliance Assurance Monitoring Regulations, Clean Air Act Amendments, 1990

Other Congressional Acts requiring CEMS or COMS include:

  • Resource Conservation and Recovery Act (RCRA) Boiler and Industrial Furnace (BIF) regulating hazardous waste incinerators in 40 CFR Part 270
  • Clean Water Act –regulating sewage sludge incinerators in 40 CFR Part 503


For more information, contact:
Alan Drake
Phone 919-707-8493