Performance Specification 2
Specifications and Test Procedures for SO2 and NOX Continuous Emission Monitoring Systems in Stationary Sources
40 CFR Part 60, Appendix B
From the method — regulatory text
Sections 1.0 and 2.0 of Performance Specification 2—Specifications and Test Procedures for SO2 and NOX Continuous Emission Monitoring Systems in Stationary Sources, as published at 40 CFR Part 60, Appendix B. Retrieved 10/07/2026. The full method is on the eCFR.
1.0 Scope and Application
1.1 Analytes
| Analyte | CAS Nos. |
|---|---|
| Sulfur Dioxide (SO2) | 7449-09-5 |
| Nitrogen Oxides (NOX) | 10102-44-0 (NO2), 10024-97-2 (NO) |
1.2 Applicability.
1.2.1 This specification is for evaluating the acceptability of SO2 and NOX continuous emission monitoring systems (CEMS) at the time of installation or soon after and whenever specified in the regulations. The CEMS may include, for certain stationary sources, a diluent (O2 or CO2) monitor.
1.2.2 This specification is not designed to evaluate the installed CEMS performance over an extended period of time nor does it identify specific calibration techniques and other auxiliary procedures to assess the CEMS performance. The source owner or operator is responsible to calibrate, maintain, and operate the CEMS properly. The Administrator may require, under section 114 of the Act, the operator to conduct CEMS performance evaluations at other times besides the initial test to evaluate the CEMS performance. See 40 CFR Part 60, § 60.13(c).
2.0 Summary of Performance Specification
Procedures for measuring CEMS relative accuracy and calibration drift are outlined. CEMS installation and measurement location specifications, equipment specifications, performance specifications, and data reduction procedures are included. Conformance of the CEMS with the Performance Specification is determined.
EssentialRegs notes
Our plain-English reading of Performance Specification 2. Not the method text.
What it measures
Whether a continuous emission monitoring system for sulfur dioxide, nitrogen oxides or both is acceptable for use, based on its installation, performance and accuracy.
How it works
The system is installed at a representative location and operated through a test period. Its calibration drift is checked repeatedly over a period of days. Its relative accuracy is determined by comparing its readings with simultaneous results from a reference test method. The system is acceptable when it meets the limits in the specification.
Equipment
The continuous emission monitoring system being certified, calibration gases, and the reference method sampling equipment used for the relative accuracy test.
When a rule cites it
Rules that require a continuous emission monitoring system (CEMS) to demonstrate compliance, report emissions or track an emission limit on an ongoing basis. The system must be certified under the specification before its data count for those purposes, and recertified when the rule or a major system change calls for it.
Notes for compliance staff
Performance Specification 2 certifies the pollutant analyzer. Oxygen and carbon dioxide monitors used to correct to a diluent basis are covered by Performance Specification 3. Ongoing quality assurance after certification is set by the rule that requires the system.
Cited by
Provisions in the corpus whose text cites Performance Specification 2. Subscribers land on the provision in the regulation reader; visitors see a preview of it (the GP05 sample opens in full).
40 CFR Part 60 Subpart OOOO
40 CFR Part 60 Subpart OOOOa
40 CFR Part 60 Subpart OOOOb
The sections marked as regulatory text above are reproduced from the CFR. Everything under ‘EssentialRegs notes’ is our reference copy, not the method. The method as published in the CFR controls.