PFCs (perfluorocarbons), covered by the Kyoto Protocol, are organofluorine compounds that contain exclusively carbon and fluorine. Examples are CF4 (tetrafluoroethane) and C2F6 (hexafluoroethane or perfluoroethane). These substances have high global warming potential but do not bioaccumulate and are considered to be of low order of toxicity. They are gases or volatile liquids.
While other compounds which contain atoms other than carbon and fluorine are also sometimes called PFCs, they should in effect be considered specifically as fluorocarbon derivatives. Examples are PFOA (perfluorooctanoic acid: C8HF15O2) and PFOS (perfluorooctanesulfonic acid : C8HF17O3S ). These are typically surfactants with long carbon chains, with uses in fluoropolymer preparations and for water repellancy.
The properties of these substances – bioaccumulation and stability – means that voluntary and regulatory measures are being taken to control their use and minimize their emissions to the environment.