PURPOSE: This SAE Recommended Practice is restricted to Mechanical Vapor Compression Refrigeration Systems driven by the vehicle or auxiliary engine@ because all presently known or proposed passenger compartment cooling systems which involve any question of safety are of that type. It is not the intention to restrict the use of@ or further development of@ other types of refrigeration systems for passenger compartment cooling. Should other systems be found practical at some future time@ this SAE Recommended Practice may be amended or an additional recommended safety practice drawn up for such other systems.