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Statutory guidance

Monitoring stack emissions: quality assurance of continuous monitoring

Guidance for operators, test laboratories and equipment suppliers on the quality assurance of continuous emissions monitoring systems (CEMS).

Updates to this page

From:
Environment Agency
Published:
7 April 2014
Last updated:
14 September 2026
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  1. In section 3.7.1, the graphs showing examples of QAL2 calibrations have been removed. In section 3.7.4, added a requirement on when repeat QAL2 is required for particulate CEMS. In section 3.7.12, the requirement to assess the difference between the average of the SRM and CEMS results has been removed. Added the use of ambient air for O2, when using procedure c. In section 3.7.16, changed virtual ELVs for CO2 and N2O. Changed variability and acceptance test criteria for dust measurements. In section 3.12, the requirements on test gases have been updated. In section 5.3, the reporting requirements for AST failures and repeat QAL2s have changed. Section 7 has been updated to reflect the changes in section 5.3.

  2. Updated sections on QAL1 requirements; Verification and calibration requirements; Frequency of QAL2 checks; Extending the calibration range; QAL2 report; QAL3 – general; AST failures; Report template.

  3. Throughout we have updated or deleted references to revised or withdrawn Environment Agency guidance, such as TGN M22. In 3.5.17 we have clarified the calibration of peripheral CEMS measurements. In 6.1 we have added an instruction to obtain approval for the continued use of a previous calibration function. In 6.8 we have added an instruction on applying new calibration functions. In appendix 3 we have added information on quality assurance and quality control procedures for automated dust arrestment plant monitors.

  4. Removed the need to conduct a QAL2 every 3 years for incineration processes.

  5. Incorporates EN14181 MID and Quick Guides 3, 5, 6 and 14. There are also changes to reflect the amendments within EN 14181:2014.

  6. First published.

Applies to England

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Monitoring stack emissions: quality assurance of continuous monitoring

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This technical guidance note provides guidance to Environment Agency staff, monitoring contractors, industry and other parties interested in continuous emission monitoring.

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