Gas compressors have a labyrinth sealing on both shaft ends to avoid gas leakage in to the atmosphere. On the contrary to mechanical seals – applied in pumps, diesel engines and most rotating machines – labyrinth seals are not leak proof. There must be constant venting of the system. For oil free air screw compressors, leakage of air is not harmful, but for gas compressors leakage of natural gas would be harmful to the environment. For safe operation, gas is fed into a stack at safe distance from the oil/gas platform.