This International Standard specifies a helium test method for detecting and localizing gas leaks in the exhaust systems of road vehicles equipped with an internal combustion engine, in order to improve the quality of exhaust gas measurements. In doing so, it completes the requirements of ISO 3929, applicable regulations and, depending on the leak rate to be detected, ISO 13556. The method is particularly applicable for use in automotive workshops, by end-of-line of automotive and exhaust parts manufacturers, in laboratories prior to exhaust emission tests, and in testing and diagnosis stations.