Halons are chemicals that contain carbon, fluorine, and bromine. They are used in fire extinguishers and other firefighting equipment. Because of their bromine content, halons can destroy ozone molecules(O₃) very effectively, thereby contributing to the depletion of ozone and the creation of holes in the ozone layer of the stratosphere. The ozone layer is located 10–28 mi (16–47 km) above the surface of the earth and it protects humans and the environment from the Sun's ultraviolet-B radiation. Halons account for approximately 20% of the ozone depletion.

Halons have been used since the 1940s, when they were discovered by U.S. Army researchers looking for a fire-extinguishing agent to replace carbon tetrachloride. Halons are very effective against most types of fires, are nonconductive, and dissipate without leaving a residue. They are also economical, very stable, and safe for human use.

Halons consist of carbon atom chains with attached hydrogen atoms that...