Vacuum in the cooling, refrigeration and air conditioning systems is to eliminate undesirable gases, mainly air and water vapor (humidity). Removing non-condensable air and gases in a system using a vacuum pump is called degassing. Eliminating the "water vapor" is called dehydration. In the refrigeration and air conditioning industry, the removal of air, plus water vapor or moisture, is called Evacuation. The vacuum in refrigeration helps us to avoid a decrease in its volumetric efficiency.