Freon is a trademark belonging to the E. I. du Pont company for a series of chlorofluorocarbons (CFCs). CFCs are organic compounds composed primarily of chlorine, fluorine, carbon, and hydrogen. These compounds are chemically stable, nontoxic, and nonflammable. Due to their high density, low boiling point, and low viscosity they are especially useful for use as refrigerants, aerosol propellants, solvents, and expansion agents in polyurethane foams. Since the 1970s, CFC use has declined due to concerns about their effects on the ozone layer.

The compounds that would become known as Freon were discovered in the 1930s by researchers for General Motors led by Thomas Midgley, Jr. They discovered that chlorine and fluorine atoms could be positioned along a hydrocarbon backbone to form molecules that functioned as efficient refrigerants. The first material they made was dichlorodifluoromethane, a compound that contains one carbon, two chlorine, and two fluorine atoms. This...