Freon is a registered trade name of DuPont, which it uses for a number of halocarbon products. They are stable, nonflammable, moderately toxic gases or liquids which have typically been used as refrigerants and as aerosol propellants. These include the chlorofluorocarbons (CFCs) implicated in ozone depletion, but also include newer refrigerants which typically include fluorine instead of chlorine and do not deplete the ozone layer.
