An official website of the United States government.

This is not the current EPA website. To navigate to the current EPA website, please go to This website is historical material reflecting the EPA website as it existed on January 19, 2021. This website is no longer updated and links to external websites and some internal pages may not work. More information »

Air Emission Measurement Center (EMC)

Technical Amendments to Procedure 6 - Final Rule


  •  On September 13, 2017, the U.S. Environmental Protection Agency (EPA) finalized minor technical amendments to a tool used to evaluate hydrogen chloride (HCl) continuous emissions monitoring systems (CEMs) – known as Procedure 6. Procedure 6 specifies the minimum quality assurance requirements necessary for the control and assessment of the quality of CEMs HCl data used for compliance with regulatory requirements.
  • Together with Performance Specification 18, Procedure 6 is used to evaluate HCl emissions for Portland Cement facilities, electric generating units, and industrial, commercial, and institutional boilers and process heaters.


  • On July 7, 2015, the EPA published Procedure 6, which is a companion to Performance Specification 18. 
  • After publication, certain minor data treatment inconsistencies were identified.
  • The EPA proposed to correct the minor inconsistencies in Performance Specification 18 and Procedure 6 through a direct final action titled, “Technical Amendments to Performance Specification 18 and Procedure 6.” 81 Fed. Reg. 31,515 (May 19, 2016). One substantive comment was received regarding changes to Procedure 6. 
  • The EPA is responding to that comment and finalizing corrections to Procedure 6 with this action.


Technical Amendments to Procedure 6- Federal Register

You may need a PDF reader to view some of the files on this page. See EPA’s About PDF page to learn more.