The measurement and test methods for the assessment of active Stage II vapour recovery systems at filling stations as specified in VDI 4205 Parts 1 through 3 for operators of filling stations, technical experts and specialist companies, as well as for inspection authorities, in order to allow the operation of the those vapour recovery systems to be determined with reference to the measurement and test methods described herein. Depending on the tasks to be performed, different methods may find application for this purpose. Measurement and test methods for the assessment of passive vapour recovery systems are not covered by this guideline.