Freon is a trade name for a group of chlorofluorocarbons used primarily as a refrigerant. The word Freon® is a registered trademark belonging to E.I. du Pont de Nemours & Company. Prior to their implication as a major contributor to the greenhouse effect, freons were also used as aerosol propellants and to foam up polymer materials. It is also implicated, along with other chlorofluorcarbons, in the depletion of the ozone layer, which protects against UV radiation.

Freon was developed as a safer alternative to toxic gases such as, ammonia (NH₃), methyl chloride (CH₃Cl), and sulfur dioxide (SO₂), that were used as refrigerants prior to the discovery of freon. Despite the controversy, R12 works well and is very safe. It's inventor, Thomas Midgley, actually breathed in a lungfull and exhaled over a candle to demonstrate its notoxicity and nonflammability.

Before CFCs were banned by developed nations, a 12 ounce can of freon (R12) cost about $11, following the ban the cost of freon rose dramatically. People now go through considerable trouble to recycle freon from existing sources. As of 2002, a pound of freon cost about $85. Freon is most frequently sold in 12 ounce cans and 30 pound cannisters.

Freon 12 ® (also known as R-12) was a popular refrigerant before it was banned. The chemical formulas is CCl₂F₂ and its proper chemical name is dichlordifluoromethane. When people refer to freon without specifying a number, it is likely that they mean freon-12.

Suva 134a ® (also known as R-134 or R-134a) is the most common replacement for R-12. Unlike R-12, which is a chlorofluorcarbon, R-134 is a hydrofluorocarbon. The chemical formula is CH₂FCF₃ and the proper chemical name 1,1,1,2-Tetrafluoroethane.

R-11	CFC-11	Trichlorofluoromethane
R-12	CFC-12	Dichlorodifluoromethane
R-13	CFC-13	Chlorotrifluoromethane
R-22	HCFC-22	Chlorodifluoromethane
R-23	HFC-23	Trifluoromethane
R-113	CFC-113	Trichlorotrifluoromethane
R-114	CFC-114	1,2-Dichloro-1,1,2,2-tetrafluoroethane
R-115	CFC-115	1-Chloro-1,1,2,2,2-pentafluoroethane
R-116	CFC-116	Hexachloroethane
R-134a	HFC-134a	1,1,1,2-Tetrafluoroethane
R-227ea	HFC-227ea	1,1,1,2,3,3,3-Heptafluoropropane

See also: Halon.