EPA PS-1 Opacity Monitoring Requirements Explained
Opacity Monitor Learning Center
EPA Performance Specification 1, commonly called PS-1, addresses continuous opacity monitoring systems used at stationary sources. It covers how an applicable system is designed, installed and evaluated. This guide explains the main responsibilities and the distinction between initial testing and ongoing quality assurance.
Does PS-1 apply to my facility?
Begin with the applicable source rule and your air permit. PS-1 does not independently require every boiler, crematory or incinerator to install a monitor. For COMS required under 40 CFR Part 60, its applicability provisions address new systems and certain replacements, relocations, substantial refurbishments or recertifications. Confirm the requirements for your specific installation with the permitting authority.
Read PS-1 in 40 CFR Part 60, Appendix B, particularly sections 1 and 2.
What does PS-1 require?
- Manufacturer verification: equipment design and performance testing, with conformance documentation, using the referenced ASTM D6216 requirements.
- Suitable installation: a measurement location and beam path that represent emissions, with attention to access and interference.
- Field performance testing: confirmation that the installed system performs acceptably.
Buying an instrument designed for PS-1 applications is one part of the process. Installation, testing and documentation remain responsibilities of the facility. The current specification references ASTM D6216-20 and includes provisions for previously certified equipment. See the current PS-1 requirements for the complete conditions.
What happens during initial field testing?
The field checks address optical alignment, calibration error at multiple test points, system response time, and averaging and recording functions. PS-1 also specifies a 168-hour operational test period, including zero and upscale drift evaluations. This period has defined source-operation conditions and restrictions on unscheduled maintenance or adjustment; a monitor failure can require restarting the test.
Use the complete test procedures and acceptance criteria when planning a certification. A brief guide cannot substitute for the required test protocol. EPA provides the PS-1 specification and supporting material.
PS-1 and Procedure 3 serve different purposes
PS-1 addresses system specifications and acceptance testing. Where applicable, 40 CFR Part 60, Appendix F, Procedure 3 addresses ongoing quality assurance for COMS used to demonstrate compliance with NSPS opacity standards.
Procedure 3 includes written QA/QC procedures, daily zero/upscale drift and status checks, periodic performance audits and annual zero alignment. It also addresses corrective actions and out-of-control periods. Its defined operating periods and conditional audit-frequency provisions matter; use the rule and permit to establish the actual schedule.
Read EPA’s Procedure 3 guidance and procedure.
What can affect opacity measurements?
Condensed water droplets can interfere with opacity measurement. Monitor placement, clear optical surfaces and correct alignment matter. An opacity value measures light attenuation; it does not identify the chemical composition of the material or automatically provide a particulate mass concentration. Review process conditions before interpreting a changed reading.
How can EMS help?
Discuss WatchDog continuous opacity monitors and the EMS WatchDog PS-1 for projects requiring PS-1 performance. EMS also provides startup, certification, opacity monitor service and audit support and neutral-density-filter certification.
Contact EMS with the applicable permit language, source type, stack dimensions and existing equipment details. EMS can help identify suitable equipment and service scope; the permitting authority determines the requirements that apply to your facility.
Educational summary prepared September 22, 2026. Consult the current rule and your facility’s permit for complete requirements. Sources: EPA Performance Specification 1, current eCFR Appendix B, and EPA Procedure 3, linked above.