This part of ISO 15011 defines a laboratory method for measuring the emission rate of ozone during arc welding, using a hood technique. The method is directed primarily at measuring ozone emission rate when using gas-shielded arc welding processes, but it can also be employed with other processes, e.g. selfshielded flux-cored arc welding, provided that welding can be performed automatically under the hood. The method can be used to evaluate the effects of welding wires, welding parameters, processes, shielding gases, test piece composition and test piece surface condition on emission rate.