Halons are bromofluorocarbons used to extinguish fires in electrical and computer systems. Examples include, bromochlorodifluoromethane and bromotrifluoromethane. All yellow fire extinguishers containing halons in Australia should have been withdrawn from use by now.
Halons were produced in much smaller amounts than CFCs but the C-Br bond is weaker than the C-Cl and therefore more easily broken. More importantly on a per atom basis, Br is 10-100 times as destructive of ozone as Cl.
The 1987 Montreal Protocol applies to halons as well as CFCs. The protocol was amended in Copenhagen in 1992 to state that production of CFCs, halons and the solvent CCl4 (carbon tetrachloride) was to cease entirely by 1996.