Preparations for the implementation of a new ozone cross section value worldwide allowing more accurate measurements of surface ozone are going to plan. The new value (CCQM.O3.2019 value) is just over 1 % lower than the current value (Hearn.1961 value) with a relative uncertainty that is reduced to 0.31%. Five key technical normative documents have been revised and published to include the new value, with a remaining three to be published in the next months. The efforts to achieve a coordinated update of normative standards has been led by the CCQM-GAWG Task Group on Ozone Cross-Section Change Management, which has also published guidelines on:

• Units and values for the ozone absorption cross section at 253.65 nm (air) with appropriate significant digits and rounding for use in documentary standards
• Recommendations for metadata provision when changing the value of the UV ozone absorption cross section
• How to implement the new absorption cross-section for ozone concentration measurements

Regulations/written standards that have recently been updated are:

• US EPA Code of Federal Regulations Part 50 Appendix D - Reference Measurement Principle and Calibration Procedure for the Measurement of Ozone in the Atmosphere (Chemiluminescence Method)
• Japanese Standard JIS B 7957:2006/AMENDMENT 1:2023 Continuous analyzers for ozone and oxidants in ambient air (Amendment 1)
• Australian Standard AS 3580.6.1 (2023), Methods for sampling and analysis of ambient air, Method 6.1: Determination of ozone - Direct-reading instrumental method
• ASTM Standard D5110-98 (2022), Standard Practice for Calibration of Ozone Monitors and Certification of Ozone Transfer Standards Using Ultraviolet Photometry
• ASTM Standard D5110-02 (2022), Standard Test Methods for Continuous Measurement of Ozone in Ambient, Workplace, and Indoor Atmospheres (Ultraviolet Absorption)

Standards that are currently under revision with updates to be published in 2024 are:

• International Standard ISO 13964 (1998), Air quality - Determination of ozone in ambient air - Ultraviolet photometric method
• International Standard ISO 10313 (1993), Ambient air - Determination of the mass concentration of ozone - Chemiluminescence method
• European Standard EN 14625 (2012), Ambient air - Standard method for the measurement of the concentration of ozone by ultraviolet photometry

Further information is available at https://www.bipm.org/en/ozone.