Stage II vapor recovery systems have been part of many gas dispensing facilities in the US. These systems are aimed at minimizing the amount of volatile components emitted to the atmosphere while fueling vehicles. Such systems are added to gas dispensers and include a pump and special set of hoses, breakaways and nozzles. Its principle of operation is that it would suction the air and gas vapors being displaced out of the gas tank by the incoming gas; these air and vapor mix then is pumped back into the underground storage tanks (UST).

The following video illustrates the operation and its limitations: