It is a requirement of environmental protection that the vapor/air mixtures formed during the storage, transport and refilling of petrols be collected and that the vapor contained in these mixtures be recovered. By vapor balancing within the distribution chain, the vapor/air mixtures are returned to the distribution depots where they are intermediately stored in vapor tanks, if need be, and processed in vapor recovery and exhaust air cleaning units. The more comprehensive the technical measures of discharging, conveying or processing the vapor/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 vapor recovery units.