The portion of the Clean Air Act that applies to the Heating, Ventilating and Air Conditioning (HVAC) industry encourages the development of ozone-friendly substitutes for chemicals that contain ozone destroying chlorine, which are called hydrochlorofluorocarbons (HCFCs). The chemical refrigerant of choice for more than four decades, referred to as R-22, is in the HCFC category. R-22 is widely used in heat pumps and AC condensing units to heat and cool homes. Today, a refrigerant called R-410A is used because of its ozone-friendly properties.