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Which Fire Extinguisher is the right one to choose? This is one of the less than clear issues in aviation.
It is a common misconception that Halon “removes oxygen from the air.” I have always wondered why you would employ an extinguisher that has the potential to suck the life right out of you.
Tree things must come together at the same time to start a fire. Fuel, oxygen and an ignition source. Traditionally, to stop a fire you need to remove one side of the triangle: Oxygen, Fuel or the Ignition source. Halon adds a fourth dimension to firefighting by breaking the chain reaction. It stops the fuel, oxygen and ignition source from working together by chemically reacting with them.
What I learned researching this article is quite interesting and I hope it can provide a little insight as to why we continue to see Halon in aircraft. I also learned the halon is not the oxygen eating monster I always thought it was.
There are lot of fire extinguisher choices that you can pick up at almost any retailer to include the grocery store. I also discovered that there a lot of differences between kitchen, auto and aviation fire extinguishers.
There are 2 basic types of portable Fire Extinguisher: Dry chemical and Halon
Dry chemical extinguishers are cheaper and easier to find than their Halon brethren. While there are many types of fire extinguishers (Foam, dry chemical, dry powder, C02, Water, Clean Agents, etc.), ABC rated dry chemical extinguishers are most common. This type of extinguisher is not intended for aviation use, but if your feet are on fire they are better than nothing.
Halon is a liquefied, compressed gas that stops the spread of fire by chemically disrupting combustion. Halon 1211 is a liquid streaming agent that leaves no residue and is remarkably safe for human exposure. Halon is rated for class “B” (flammable liquids) and “C” (electrical fires). Halon is also effective on class “A” (common combustibles) fires. Halon 1211 is a low-toxicity, chemically stable compound that, as long as it remains contained in the cylinder is easily recyclable.
Halon has not been manufactured since 1994. However due to widespread use over many years, there continues to be a regular supply of used Halon 1211 fire extinguishers available for recycling. New halon fire extinguishers are still available for purchase. 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.
There are three other environmentally friendly options to Halon: Halatron 1, FM-200 and FE-36. While they work very well and are less harmful to the environment (i.e. depletion of the ozone layer; global warming) when released they require almost 2 times the agent. That means a bigger bottle at twice the weight.
Inhaling Fire Extinguishing Agents
The FAA took a hard look at the effects of extinguishing agents in cockpits and here is what the FAA has to says regarding Halon: According to FAA Advisory Circular AC 120- 80, In-Flight Fires, “NTSB investigations of in-flight fires indicate that crewmembers have been hesitant to use Halon extinguishers during flight because of mistaken ideas about adverse effects of Halon.” The FAA notes, “The toxic effects of a typical aircraft fire, for example, far outweigh the potential toxic effects of discharging a Halon fire extinguisher.”
Here is what the FAA says about dry chemical agents discharged in the enclosed space of an aircraft: According to AC 20-42C, Hand Held Fire Extinguishers for Use in Aircraft: “Dry chemical extinguishing agents when discharged in crew compartments of confined areas may cause serious impairment to visibility. In addition, they may cause temporary breathing difficulty during and immediately after discharge.” Another caveat is the dry chemical agent can be very corrosive to airplane parts. The dry chemical agent usually used in them is either sodium bicarbonate or monoammonium phosphate. According to the National Fire Protection Association “Any chemical powder can produce some degree of corrosion or other damage, but monoammonium phosphate is acidic and corrodes more readily than other dry chemicals.”
The FAA does not provide a list of authorized fire extinguishers for aircraft. According to AC 20-42D, “Hand Fire Extinguishers for Use in Aircraft, which provides methods acceptable to the Administrator for showing compliance with the hand fire extinguisher provisions in Parts 25, 29, 91, 121, 125, 127, and 135 of the FAR.”
“The FAA accepts hand fire extinguishers approved by Underwriters Laboratories, Inc.”
“For occupied spaces on aircraft, Halon 1211 extinguishers should not be less than 2½ pounds (1.2kg) capacity. These extinguishers should have a minimum 5B: C rating; not less than 8 seconds effective discharge time; not less than a 10 ft. (3 meter) range, and may be equipped with a discharge hose.”
New fire extinguishers do not require an 8130-3 because it is not considered a part of the aircraft.
I cannot and will not tell someone which extinguisher to use. That’s a personal choice. The FAA does not mandate which one you choose, if any at all. But if I were asked which fire extinguisher I would choose, my vote would be hands down Halon.
Inspection and Maintenance
The vast majority of fire extinguishers in the USA are UL Listed – in fact, this is a legal requirement in most states. All UL listed fire extinguishers reference the National Fire Protection Association (NFPA) code 10 for inspection and maintenance requirements.
NFPA 10 directs that extinguishers be inspected every 30 days or more often to check that they are in working order (e.g. fully charged, undamaged, accessible). Ensuring that the extinguisher is fully charged is crucial, since fire extinguishers can and do leak. If your extinguisher has a pressure gauge, a quick glance is all that is needed. Some “disposable type” Halon extinguishers do not have a gauge. Though NFPA 10 allows for these units to simply be “hefted” to get a sense of whether or not they are charged, physically weighing the unit is the only sure way to tell, since it can be difficult to notice leakage of a few ounces. The UL nameplate on the extinguisher specifies the minimum gross weight required for the extinguisher to be acceptable.
An annual weight check is required for all extinguishers, and gauged, rechargeable extinguishers require professional maintenance every 6 years. Regularly maintained rechargeable halon fire extinguishers have been known to outlast the useful life of the aircraft in which they have been installed!