---

Halons: Fanning The Flames

Of all the chemical groups controlled under the Montreal Protocol, halons have the highest ozone-depletion potential (ODP). Used mainly for fire suppression, halons contain bromine which is 40-60 times more effective at destroying ozone than the chlorine found in CFCs. Halon 1211 (bromochlorodifluoromethane) is used in portable fire extinguishers where a spray is directed at a distinct and isolated fire source. It has an ODP of 3 (CFC11 has an ODP of 1) and an atmospheric lifetime of 25 years. Halon 1301 (bromotrifluoromethane) is used in fixed fire suppression systems as a gas. It has an atmospheric lifetime of 110 years, and with an ODP of 10 is by far the most ozone-damaging chemical. Halon 2402, the least used of the three, has an atmospheric lifetime of 28 years and an ODP of 6. Because of the inherent danger posed by halons, the chemicals were the first group to be controlled under the Montreal Protocol, with a ban on use and importation in Article 2 countries coming into force at the start of 1994.2 Yet production in Article 5 parties, now mainly limited to China and Korea, can continue until 2010. Recent scientific research by the US National Oceanic and Atmospheric Administration has highlighted increasing concentrations of halons in the atmosphere, despite the production ban in non-Article 5 parties being in place for almost five years. While replacements exist for practically all halon 1211, for halon 1301 there are still a number of essential use exemptions. As this gas is an effective fire suppressant and replacements are often needed in greater volumes to do the same job, halon 1301 is still widely used in the military, aerospace, shipping and, to a lesser extent, the oil and gas industries.

---