Bromochlorodifluoromethane (BCF), also referred to by the code numbers Halon 1211 and Freon 12B1, is a

haloalkane The haloalkanes (also known as halogenoalkanes or alkyl halides) are alkanes containing one or more halogen substituents. They are a subset of the general class of halocarbons, although the distinction is not often made. Haloalkanes are widely u ...

with the chemical formula C F₂ Cl Br. It is used for fire suppression, especially for expensive equipment or items that could be damaged by the residue from other types of extinguishers.

Use as a fire extinguishing agent

Brominated haloalkanes were first used during World War II in fire extinguishers for aircraft and

tank A tank is an armoured fighting vehicle intended as a primary offensive weapon in front-line ground combat. Tank designs are a balance of heavy firepower, strong armour, and good battlefield mobility provided by tracks and a powerful ...

s. BCF was introduced as an effective gaseous fire suppression agent in the mid-1960s for use around highly valuable materials in places such as

museum A museum ( ; plural museums or, rarely, musea) is a building or institution that cares for and displays a collection of artifacts and other objects of artistic, cultural, historical, or scientific importance. Many public museums make th ...

mainframe A mainframe computer, informally called a mainframe or big iron, is a computer used primarily by large organizations for critical applications like bulk data processing for tasks such as censuses, industry and consumer statistics, enterprise ...

rooms, and telecommunication switching centers. BCFs were also widely used in the maritime industries in the engine rooms of ships and also in the transport industry in vehicles. Its efficiency as a fire extinguishing agent has also led it to be the predominant choice of fire extinguishing agent on commercial aircraft and is typically found in cylindrical hand-held canisters. Its advantages as a fire extinguishing agent are that it has lower toxicity than chemicals such as

carbon tetrachloride Carbon tetrachloride, also known by many other names (such as tetrachloromethane, also recognised by the IUPAC, carbon tet in the cleaning industry, Halon-104 in firefighting, and Refrigerant-10 in HVACR) is an organic compound with the chemi ...

and that since it is a covalently bonded compound, it does not form conductive ions, therefore being usable on electrical equipment. BCF is an excellent fire extinguishing agent, as it is a streaming agent with low toxicity, a low pressure, liquefied gas, and effective on all common types of fires, A, B, and C. It is mainly used in portable and wheeled extinguishers, and small spot protection units for aviation and marine engine applications, and was never widely used in fixed systems like Halon 1301 was. BCF has fairly low toxicity. The lethal concentration for 15 minute exposure is about 32%.

Synthesis

BCF is commercially synthesized in a two-step process from

chloroform Chloroform, or trichloromethane, is an organic compound with formula C H Cl3 and a common organic solvent. It is a colorless, strong-smelling, dense liquid produced on a large scale as a precursor to PTFE. It is also a precursor to various ...

. Chloroform is

fluorinated In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers ...

with

hydrogen fluoride Hydrogen fluoride (fluorane) is an inorganic compound with the chemical formula . This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock ...

. The resulting chlorodifluoromethane is then reacted with elemental

bromine Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table ( halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simi ...

at 400-600 °C, with reaction time limited to about 3 seconds. The overall yield is over 90%.

Regulation

The production of BCF and similar

chlorofluorocarbon Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and p ...

s has been

banned A ban is a formal or informal prohibition of something. Bans are formed for the prohibition of activities within a certain political territory. Some bans in commerce are referred to as embargoes. ''Ban'' is also used as a verb similar in meanin ...

in most countries since January 1, 1994 as part of the

Montreal Protocol The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion. It was agreed on 16 September 1987, and entered into force ...

on ozone depleting substances. However, recycling of Halon 1211 allows it to remain in use, although parts availability is limited to a few manufacturers and can be an issue. Halon 1211 is still widely used in the United States, despite its high cost, with the US Military being the biggest user, but Europe and Australia have banned its use for all but "critical applications" such as aviation, military, and police use. The manufacture of UL Listed halon 1211 extinguishers was supposed to cease on October 2009. The future listing is still in discussion. Halotron I, the replacement extinguishing agent, requires a larger volume to get the same ratings as 1211.

Gallery

File:H-1211 mm.png, H-1211 measured by the Advanced Global Atmospheric Gases Experiment
AGAGE
in the lower atmosphere (

troposphere The troposphere is the first and lowest layer of the atmosphere of the Earth, and contains 75% of the total mass of the planetary atmosphere, 99% of the total mass of water vapour and aerosols, and is where most weather phenomena occur. Fro ...

) at stations around the world. Abundances are given as pollution free monthly mean mole fractions in parts-per-trillion. File:Halon 1211 Fire Extinguisher.jpg, Halon 1211 Fire Extinguisher, USA, early 1990s. File:Aviation H3R Halon 1211 fire extinguisher.jpg, A portable aviation Halon 1211 fire extinguisher, USA, 2015.

References

External links