What Is A CEMS?
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 U.S. EPA and IDEM regulations for determinations of continuous compliance with standards, annual total emissions relative to the federal Acid Rain program, and air pollutant reductions required by state programs.
Performance specifications listed in the Code of Federal Regulations (CFR) at 40 CFR 60, Appendix B and 40 CFR 75 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 40 CFR 60, Appendix F and state rules in the Indiana Administrative Code (IAC) at 326 IAC 3-5 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 continuous compliance with the emission standards.
What Is A COMS?
A continuous opacity monitoring system (COMS) is the total equipment necessary for determining light transmittance passing through a flue gas or for measuring the optical density of the flue gas. The analyzer electronically converts the optical density, based on certain parameters, into an opacity reading expressed as % opacity.
Performance specifications listed in 40 CFR 60, Appendix B are used for evaluating the acceptability of the COMS at the time of, or soon after installation, and whenever specified in the regulations. Quality assurance procedures in 40 CFR 60, Appendix F and 326 IAC 3-5 are used to evaluate the effectiveness of QC and QA procedures and the quality of data produced by any COMS that is used for determining continuous compliance with the opacity standards.
CEMS/COMS Forms, Guidance, and Information
- Chapter 1 - Compliance Branch COMS Guidance Manual [ZIP]
- Chapter 2 - Compliance Branch CEMS Guidance Manual [ZIP]
- CEMS-COMS Example QA QC Plan [PDF]
- CEMS Report Format and instructions
- Relative Accuracy Test Audit (RATA) Notification Protocol (State Form 55059, available on the IDEM Forms page) - Required for CEMS testing. The completed form may be submitted by U.S. mail, email, or fax to the Compliance Data Section in IDEM’s Office of Air Quality. Forms must be received by the Compliance Data Section at least 35 days before the proposed test day.
Many facilities use professional air emissions testing services for CEMS/COMS testing. IDEM maintains a list of environmental consultants [PDF].
Compliance assistance is available upon request.