It is a requirement of environmental protection that the vapour/air mixtures formed during the storage, transport and refilling of petrol be collected and that the vapour contained in these mixtures be recovered. By vapour balancing within the distribution chain, the vapour/air mixtures are returned to the distribution depots where they are intermediately stored in vapour tanks, if need be, and processed in vapour recovery and exhaust: air cleaning units. The more comprehensive the technical measures of discharging, conveying or processing the vapour/air mixtures of flammable liquids, the greater the problems of explosion protection. In this contribution, petrol will serve as an example to present and elucidate the explosion protection measures to be taken in exhaust air cleaning or vapour recovery units.