Ozone levels in the troposphere continue to be measured at undesirable levels for human health and play an important role in climate change. Measurements of ozone at most ground level air monitoring stations utilize ultra-violet (UV) photometry which is dependent on a well-known absorption cross-section coefficient at the 253.65 nm wavelength. The ozone absorption coefficient widely accepted around the world is the Hearn value from 1961. Since this time, however, much research has been done to determine a more accurate value for use in ozone photometric instrumentation. A recent publication examines all research data gathered at the 253.65 nm wavelength since 1959 and has proposed a new value with a lower uncertainty. The Gas Analysis Working Group under the International Committee of Weights and Measures has created a task group to implement this new ozone absorption coefficient with the goal of developing a plan and timetable for a globally coordinated effort to make the change. This task group will determine the best approach for managing the process by examining the challenges to regulation changes, standards, field instrument calibration, and long-term databases. This presentation will outline the challenges ahead for the air monitoring, air pollution regulation, air modeling, and ozone instrumentation communities.
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