For the refrigeration system to work property, it must be free of air and moisture. The process by which air and moisture are removed is known as evacuation and dehydration. Moisture and air are harmful to the system because they increase the condensing temperature, raise the discharge gas temperature, cause oil breakdown and the formation of acids. Acids are corrosive to the components in the refrigeration system, including the piping, refrigerant specialties, and the which can cause mechanical failure of the compressor.