Freon is a brand name of refridgerants used in car (and home) air conditioning units. Originally developed in the 1920s as a chlorofluorocarbon (CFC), studies have found chlorofluorocarbons to be responsible for ozone depletion. Refrigerants today are now comprised of fluorine instead of chlorine, which do not deplete ozone. Still, the name Freon is used synonymously with the refrigerant you use in your car.