Vapor Recovery is the process of recovering vapors that normally would be discarded by releasing to the atmosphere or flaring off during an offloading process. Due to EPA regulations releasing gasses into the atmosphere is no longer cheaper than recovery. Monitoring the activity of the compressor as it pumps vapor from one tank to the other may be useful for safety purposes. Knowing when your compressor is flowing or not flowing can let the operator know when it is time to disconnect and move to the next tank.