Emissions Auditing - CEMS and COMS


Some Nevada facilities, such as coal-fired power plants, are required to install Continuous Emissions Monitoring Systems (CEMS) to monitor emissions on a continual basis. CEMS can monitor a variety of air pollutants, depending on the requirements for each facility.

Emissions monitored by CEMS include:

sulfur dioxide
nitrogen oxides
carbon monoxide
carbon dioxide
particulate matter
volatile organic compounds

Installing and operating a CEMS is a complex and expensive undertaking. As a result of these permitting requirements, the Bureau of Air Pollution Control approves the location and operation of these monitors and reviews and evaluates the validity of the data collected. The emissions data obtained, provides a continuous record that can be used to determine compliance with the permit requirements.

CEMS Audits

Nevada’s Bureau of Air Quality Planning reviews and evaluates facilities CEMS quarterly reports, annual Relative Accuracy Test Audit (RATA) test protocols and test reports to determine facilities’ compliance with the State and Federal applicable regulations (i.e., 40 CFR Part 60 and Part 75). The 40 CFR Part 75 regulations are more stringent and applicable to power generation facilities only.

The facilities are also required to develop a Quality Assurance/Quality Control (QA/QC) plan meeting the requirements stated in 40 CFR Part 60 Appendix F and 40 CFR Part 75 Subpart C §75.21 respectively. The plan includes written procedures which should describe in detail, complete, step-by-step procedures and operations for each of the following activities:

calibration of CEMS
calibration drift (CD) determination and adjustment of CEMS
preventive maintenance of CEMS (including spare parts inventory)
data recording
accuracy auditing procedures including: Sampling and analysis methods, program of corrective action for malfunctioning of CEMS, etc.


Some Nevada facilities are also required to install Continuous Opacity Monitoring Systems (COMS) to monitor opacity emissions on a continual basis. The Bureau of Air Quality Planning reviews and evaluates facilities COMS reports as appropriate in reference to 40 CFR Part 60 and Part 75.

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