What is Halon and How Does it Work?
Halon is a "Clean Agent." The National Fire Protection Association defines, a "Clean Agent" as "an electrically non-conducting, volatile, or gaseous fire extinguishant that does not leave a residue upon evaporation."
Halon is a liquefied, compressed gas that stops the spread of fire by chemically disrupting combustion. Halon 1211 (a liquid streaming agent) and Halon 1301 (a gaseous flooding agent) leave no residue and are remarkably safe for human exposure. Halon is rated for class "B" (flammable liquids) and "C" (electrical fires), but it is also effective on class "A" (common combustibles) fires. Halon 1211 and Halon 1301 are low-toxicity, chemically stable compounds that, as long as they remain contained in cylinders, are easily recyclable.
Halon is an extraordinarily effective fire extinguishing agent, even at low concentrations. According to the Halon Alternative Research Corporation. "Three things must come together at the same time to start a fire. The first ingredient is fuel (anything that can burn), the second is oxygen (normal breathing air is ample) and the last is an ignition source (high heat can cause a fire even without a spark or open flame). Traditionally, to stop a fire you need to remove one side of the triangle - the ignition, the fuel or the oxygen. Halon adds a fourth dimension to fire fighting - breaking the chain reaction. It stops the fuel, the ignition and the oxygen from dancing together by chemically reacting with them."
A key benefit of Halon, as a clean agent, is its ability to extinguish fire without the production of residues that could damage the assets being protected. Halon has been used for fire and explosion protection throughout the 20th century, and remains an integral part of the safety plans in many of today's manufacturing, electronic and aviation companies. Halon protects computer and communication rooms throughout the electronics industry, it has numerous military applications on ships, aircraft and tanks and helps ensure safety on all commercial aircraft.
Because Halon is a CFC, production of new Halon ceased in 1994. There is no cost effective means of safely and effectively disposing of the Halon. Therefore, recycling and reusing the existing supply intelligently and responsibly to protect lives and property is the wisest solution.
Why is Halon the best choice?
Fire needs three elements to prosper: fuel, oxygen and heat. The most common extinguishing agents like water, carbon dioxide, dry chemical and foams attack the fire physically to deprive the fire of one or more of the three critical elements needed for propagation. Halon differs in the way it puts out the fire. It offers some of water's cooling effect and some of carbon dioxide's smothering action, but its essential extinguishing technique lies in its capacity to chemically react with the fire's components. It actually interrupts the chain reaction of fire.
Water is very effective on class A fires (common combustibles like wood and paper). Halon is effective on common combustibles (although not as effective as water), but Halon is also effective on class B (flammable liquids), and it does not conduct electricity back to the extinguisher operator (class C).
Halon is similar to CO2 in that it is suitable for use in cold weather and leaves no residue. Unlike CO2, however, Halon does not displace the air out of the area where it is dispensed. Even for the toughest fires, less than an 8% concentration of Halon by volume is required, leaving plenty of air to use in the evacuation process. Also, unlike CO2, there is no danger of "cold shocking" avionics or other sensitive electrical equipment.
Dry chemical fire extinguishers are effective on A, B and C class fires. However, they are highly corrosive, and create billowing clouds of choking dust, dry chemical extinguishers should not be used in an aviation environment.
Foam extinguishers are effective on class A and B fires, and are particularly useful for preventing ignition of flammable liquid spills. However, foams are inferior to Halon in that they do require cleanup and in that they are not for use on electrical fires.
Halon 1211 is a liquefied gas which, when discharged, leaves the nozzle in a stream that is about 85% liquid and 15% gas. This gives the agent a range of 9 to 15 feet and offers significant advantages in fighting fires in large aircraft cabins. Mixtures of Halon 1211 and Halon 1301 have discharge characteristics dependent on the component weight ratio.
Related FAR Sections and CFR.
a. FAR 21.305 b. FAR 23.561 c. FAR 25.561, 25.851 d. FAR 27.561 e. FAR 29.561, 29.851, 299.853(e) & (f) f. FAR 91.193(c)
g. FAR 121.309(c) h. FAR 125.119(b) i. FAR 127.107(c) j. FAR 135.155. k. Title 46 and 49 of the CFR
Is Halon still legal?
Because Halon is a CFC, the production of Halon ceased on January 1, 1994, under the Clean Air Act. There is no cost-effective means of safely and effectively disposing of the Halon that has already been produced, therefore recycling and reusing the existing supply intelligently and responsibly to protect lives and property is the best solution.
The EPA recognizes that that Halon remains the most effective "clean" extinguishing agent available, despite its ozone depleting potential, and there are no federal or state regulations prohibiting the buying, selling or use of Halon extinguishers. All Halon available now is recycled so it is an environmentally responsible choice.
How long will the supply of Halon last?
While the production of Halon ceased on January 1, 1994, under the Clean Air Act, it is still legal to purchase and use recycled Halon and Halon fire extinguishers. In fact, the FAA continues to recommend Halon fire extinguishers for aircraft.
At H3R Clean Agents, we are certain that the eventual demise of Halon will come not from insufficient supply, but from the development of an equally effective agent that does not damage the ozone layer and is relatively inexpensive. No such agent is currently available.
How safe is Halon?
Halons are low-toxicity, chemically stable compounds that have been used for fire and explosion protection from early in the last century. Halon has proven to be an extremely effective fire suppressant. Halon is clean (i.e. leaves no residue) and is remarkably safe for human exposure. Halon is a highly effective agent for firefighting in closed passenger carrying areas. Due to its effectiveness and relatively low toxicity, the FAA continues to recommend or require Halon extinguishers for use on commercial aircraft.
Extensive toxicity evaluations have been compiled by nationally recognized United States medical laboratories and institutions on Halon 1301 and Halon 1211. These evaluations have shown that Halon 1301 and Halon 1211 are two of the safest clean extinguishing agents available. Dual Halon concentrations of about 5% by volume in air are adequate to extinguish fires of most combustible materials. This concentration is equivalent to emptying twelve 2.5 lb. units in a closed room of 1000 cubic feet, which would be highly unlikely.
Does Halon remove oxygen from the air?
It is a common misconception that Halon, like CO2, "removes oxygen from the air."
According to the Halon Alternative Research Corporation (www.harc.org): "Three things must come together at the same time to start a fire. The first ingredient is fuel (anything that can burn), the second is oxygen and the last is an ignition source. Traditionally, to stop a fire you need to remove one side of the triangle-the ignition, the fuel or the oxygen. Halon adds a fourth dimension to fire fighting-breaking the chain reaction. It stops the fuel, the ignition and the oxygen from working together by chemically reacting with them."
Is Halotron 1 a type of Halon?
Halotron 1 is a "clean" fire-extinguishing agent intended to replace Halon 1211. NFPA 2001, "Standard on Clean Agent Fire Extinguishing Systems" defines a "Clean Agent" to be "an electrically non-conducting volatile, or gaseous fire extinguishant that does not leave a residue upon evaporation." Halotron is a safe, effective, environmentally acceptable replacement for Halon 1211. It is discharged as a liquid that rapidly evaporates. Halotron 1 is a proprietary three-component chemical blend based on HCFC-123.
Where can I get more information about Halon and other clean agents?
www.nafed.org - National Association of Fire Equipment Distributors
www.fssa.net - Fire Suppression Systems Association
www.harc.org - Halon Alternatives Research Corporation
FINAL RULE SUMMARY EPA BAN ON HALON MARCH 5, 1998 (63FR 11084)
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