Halon

Description

[Great Lakes Chemical] A brand name for a series of chlorofluorocarbon gases that were once widely used as fire extinguishing agents. Halon gases decompose at high temperatures to release halogen atoms that react with hydrogen atoms thereby depriving the fire of a necessary combustion component. Examples of halon compounds are:

- Halon: dichlorodifluoromethane, CCl2F2.

- Halon 1211: bromochlorodifluoromethane, CBrClF2.

- Halon 1301: trifluorobromomethane, CBrF3.

The term Halon has been commonly applied to many fire extinguishing systems that use Halon gas. In 1987, an international agreement, Montreal Protocol, mandated the phaseout of the use of Halon 1301 gas by the year 2000 because halocarbons deplete the Ozone layer.

Alternative fire extinguishing agents include Water, inert gases (Argon, Carbon dioxide, etc.) or synthetic fluorocarbon replacement gases (FM-200, FE-13 and CEA-410).

The name Halon is also used by Allied Signal for a halocarbon polymer of tetrafluoroethylene that is chemically similar to Teflon®.

Synonyms and Related Terms

dichlorodifluoromethane; bromochlorodifluoromethane; trifluorobromomethane; FM-200 [Great Lakes Chemical]; FE-13 [DuPont]; CEA-410 [3M]

Other Properties

Halons are effective on Class A (organic solids), Class B (flammable liquids) and Class C (electrical) fires. They should not be used on Class D (metal) fires because of explosion risk.

Hazards and Safety

Overexposure may cause dizziness, seizures, unconsciousness due to reduced oxygen levels. May decompose in flames to form toxic fumes.

Additional Information

B.Roberts, "Fire Suppression and Life without Halon", WAAC Newsletter, 15(2), May 1993, pp. 31-33.

Authority

• Thomas Gregory, The Condensed Chemical Dictionary, Reinhold Publishing, New York, 3rd ed., 1942

• Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993

• The Merck Index, Martha Windholz (ed.), Merck Research Labs, Rahway NJ, 10th edition, 1983

• Encyclopedia Britannica, http://www.britannica.com Comment: "halon." Encyclopædia Britannica. 2004. Encyclopædia Britannica Premium Service. 2 Dec. 2004 .

• Wikipedia, the free encyclopedia, at http://www.wikipedia.com Comment: http://en.wikipedia.org/wiki/Halon (accessed Nov. 30, 2004)