Reference Measurement Principle and Calibration Procedure for the Measurement of Ozone in the Atmosphere (Chemiluminescence Method)

Document Headings Document headings vary by document type but may contain the following: the agency or agencies that issued and signed a document the number of the CFR title and the number of each part the document amends, proposes to amend, or is directly related to the agency docket number / agency internal file number the RIN which identifies each regulatory action listed in the Unified Agenda of Federal Regulatory and Deregulatory Actions See the Document Drafting Handbook for more details. Environmental Protection Agency 40 CFR Part 50 [EPA-HQ-OAR-2022-0007; FRL-9344-02-OAR] RIN 2060-AV63 AGENCY: Environmental Protection Agency (EPA). ACTION: Final rule. SUMMARY: The Environmental Protection Agency (EPA) is finalizing an update to the current ozone absorption cross-section to the recommended consensus-based cross-section value of 1.1329x10 −17 cm 2 molecule −1 or 304.39 atm −1 cm −1 , with an uncertainty of 0.94 atm −1 cm −1 . The new value is 1.2% lower than the current value of 308 atm −1 cm −1 and reduces the uncertainty in the value to 0.31%. The adoption of this updated ozone absorption cross-section could result in increases in measured ozone concentrations but given the existing sources of potential variability in monitoring data, it is unlikely that there will be any consistent measurable and predictable effect on reported data. The EPA is also updating the dates of publication for two references associated with the updated cross-section value, adding a new reference, and making a technical correction to move three figures inadvertently placed in section 6.0 References to a new section 7.0 Figures. DATES: This final rule is effective on November 13, 2023. ADDRESSES: The EPA has established a docket for this action under Docket ID No. EPA-HQ-OAR-2022-0007. All documents in the docket are listed on the https://www.regulations.gov website. Although listed in the index, some information is not publicly availab…