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Halon Fire Systems:
Bromochlorodifluoromethane (CBrClF2) otherwise known as Halon 1211, and Bromotrifloromethane (CBrF3) Halon 1301, are the "Halon" compounds most commonly used in the fire extinguishers. Commonly Halon fire extinguishers are found in facilities such as computer rooms, around communications equipment, in chemistry laboratories and in my roll bar mounted hand held fire extinguisher. These compounds are known for low-toxicity, and are chemically stable compounds that have been used for fire and explosion protection throughout the past century. Halons have proven to be extremely effective fire suppressants, which are clean (leave no residue) and remarkably safe for human exposure.
When used properly, Halons have an excellent fire fighting record with little, if any, risk. As a synthetic organic chemist, I have personally been IN the laboratory when it was necessary to extinguish a chemical fire by setting off the Halon system - a whole room extinguisher system that would flood the room with Halon. Breathing, while flooding the sealed room, was not impaired what so ever. I would not hesitate to set it off in my car or someone else's car to extinguish a fire.
So, with that out of the way, under what conditions would one select 1211 (CF2ClBr) over 1301 (CBrF3), because at room temperature (unless you live in the Antarctic), both will exist in the gaseous state.
1. Halon 1211 (Boiling Point of 28 F) is a liquefied gas. When discharged through a fire extinguisher nozzle it comes out in a stream that is about 85 percent liquid and 15 percent gas. This gives the agent a range of 9-to-15 feet and offers significant advantages in fighting fires in "large" spaces (i.e. you can "aim" the fire extinguisher at the base of the fire source). You will normally see these hand held extinguishers equipped with a hose (for obvious reasons). Because of the "high" BP, these extinguishers are pressurized with Nitrogen gas.
2. Halon 1301 (Boiling Point -72 F) is gaseous upon discharge from a fire extinguisher nozzle and therefore has a more limited throw range. It is often used in "smaller" confined areas (i.e. used to "flood" an area like a passenger compartment of a car).
So, for our applications - small confined spaces - the halogenated methane of choice is Halon 1301.
If I had an in-car system that was Halon 1211, I would just make sure the discharge nozzle was not pointed at my face (ouch!).
You might come across a system containing a mixture of 1211 and 1301. This Halon blend is considered superior to the 1211 Halon propelled by nitrogen because it generates its own pressure (i.e. the 1301) so the extinguisher will not run out of throwing power even if the extinguisher is almost empty.
But don't get too hung up over the different types of Halon systems, remember, both 1211 and 1301 exist as gases at RT, both are halogenated methane's, both react in a similar manner with fire, both produce similar decomposition products, and therefore, both have similar precautions with respect to human exposure (remember everything is "toxic", even table salt). You can let cost be one of the determining factors in your selection.
Disclaimers: Use these fire suppressant systems at your own risk, I assume no liability or responsibility for injury to property or persons.
Article written by:
Ted R. Schwartz
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