Bromochlorodifluoromethane (BCF), also referred to by the code numbers Halon 1211 and

Freon Freon ( ) is a registered trademark of the Chemours Company and generic descriptor for a number of halocarbon products. They are stable, nonflammable, low toxicity gases or liquids which have generally been used as refrigerants and as aerosol p ...

12B1, is a

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

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. It is stored as a liquid under pressure and vaporizes when discharged to suppress fires. The use of halons, including Halon 1211, has decreased over time due to their adverse impact on the ozone layer. Alternatives have been developed to mitigate environmental concerns while still providing effective fire suppression capabilities.

Use as a fire extinguishing agent

Brominated haloalkanes were first used during World War II in

fire extinguisher A fire extinguisher is a handheld active fire protection device usually filled with a dry or wet chemical used to extinguish or control small fires, often in emergencies. It is not intended for use on an out-of-control fire, such as one which ha ...

s 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 battlefield mobility provided by tracks and a powerful engine; ...

s. BCF was introduced as an effective

gaseous fire suppression Gaseous fire suppression, also called clean agent fire suppression, is the use of inert gases and chemical agents to extinguish a fire. These agents are governed by the National Fire Protection Association (NFPA) Standard for Clean Agent Fire Ex ...

agent in the mid-1960s for use around highly valuable materials in places such as

museum A museum is an institution dedicated to displaying or Preservation (library and archive), preserving culturally or scientifically significant objects. Many museums have exhibitions of these objects on public display, and some have private colle ...

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, enterpris ...

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 carbon tet for short and tetrachloromethane, also IUPAC nomenclature of inorganic chemistry, recognised by the IUPAC), is a chemical compound with the chemical formula CCl4. It is a n ...

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 (often abbreviated as TCM), is an organochloride with the formula and a common solvent. It is a volatile, colorless, sweet-smelling, dense liquid produced on a large scale as a precursor to refrigerants and po ...

. Chloroform is

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

with

hydrogen fluoride Hydrogen fluoride (fluorane) is an Inorganic chemistry, inorganic compound with chemical formula . It is a very poisonous, colorless gas or liquid that dissolves in water to yield hydrofluoric acid. It is the principal industrial source of fluori ...

. The resulting

chlorodifluoromethane Chlorodifluoromethane or difluoromonochloromethane is a hydrochlorofluorocarbon (HCFC). This colorless gas is better known as HCFC-22, or R-22, or . It was commonly used as a propellant and refrigerant. These applications were phased out under ...

is then reacted with elemental

bromine Bromine is a chemical element; it has chemical symbol, symbol Br and atomic number 35. It is a volatile red-brown liquid at room temperature that evaporates readily to form a similarly coloured vapour. Its properties are intermediate between th ...

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 Halogenation, halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F). They are produced as volatility (chemistry), volat ...

s has been banned in most countries since January 1, 1994 as part of the

Montreal Protocol The Montreal Protocol on Substances That Deplete the Ozone Layer 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 ...

on ozone depleting substances. Halon 1211 is also a potent greenhouse gas with a 100-year

global warming potential Global warming potential (GWP) is a measure of how much heat a greenhouse gas traps in the atmosphere over a specific time period, relative to carbon dioxide (). It is expressed as a multiple of warming caused by the same mass of carbon dioxide ( ...

2,070 times that of carbon dioxide and an

atmospheric lifetime Greenhouse gases (GHGs) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. Unlike other gases, greenhouse gases absorb the radiations that a planet emits, resulting in the greenhouse effect. T ...

of 16.0 years. 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. 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 in October 2009. The future listing is still in discussion.

Halotron I Halotron I is a fire extinguishing agent primarily composed of a raw material HCFC-123 (93%), mixed with tetrafluoromethane and argon serving as propellants. Global emission concerns Halotron I was originally introduced in 1992 as a replacement ...

, 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 lowest layer of the atmosphere of Earth. It contains 80% of the total mass of the Atmosphere, planetary atmosphere and 99% of the total mass of water vapor and aerosols, and is where most weather phenomena occur. From the ...

) 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