The aim of the project is to investigate, compare, and if needed, further develop test methods for measuring the ozone emission rates during welding. Ozone emission rate data are produced using the most applicable methods identified though a critical literature review. In parallel, welders exposure to ozone are measured under carefully controlled conditions. The method(s) which provide the best correlation between ozone emission rate and exposure to ozone at the workplace is identified and, if needed, further developed. The method(s) is validated in round robin tests. A revised draft standard for ozone emission rate measurement is produced and presented to CEN/TC 121.