Due to the physical property of warm air to absorb more moisture than cold air this method reduces the dew point of the pressure by cooling the compressed air. It is usually fixed between +0.3°C and +3°C to avoid freezing of the surface of the heat exchanger. In the air/air-heat exchanger the air flowing in heats the cooled compressed air flowing out. By this the own temperature already decreases, and condensate already forms. In the air/coolant-heat exchanger the compressed air is cooled down to the value entered at the control penal. The condensate that is produced here and consists of water and oil is drained off via a trap to the outside. There the condensate is separated in water and oil.