Air conditioning systems use a refrigerant to replace hot with cold air. The refrigerant is sent in a loop where it absorbs heat inside, removes it on the outside and cools it before it enters the inside again, according to LiveScience.
Air conditioning systems have five parts: an evaporator, a compressor, a condenser, a fan and a chemical refrigerant. The compressor sends the refrigerant to the condenser coil in a high-pressure, high-temperature gaseous state. The refrigerant passes through the condenser coil where it is exposed to cool outside air that absorbs its heat. The cool air forces the refrigerant into a high-pressure, high-temperature liquid state before it reaches the expansion valve.
The expansion valve controls the refrigerant flow to the evaporator coil. The evaporator coil receives indoor air from a blower, the refrigerant absorbs the heat from the air, and the cooled air is delivered to the air conditioned area through ducts. The refrigerant is then sent back to the compressor where the loop starts over again.
The chemicals most often used as refrigerants are R-22 and R-410A. Chemically, they are called hydrochlorofluorocarbons or HCFCs. Their ability to transform from a liquid to a gaseous state is what makes them useful as refrigerants.