In this article I make the case that a clean agent fire extinguisher – preferably halon - is a must for your plane and hangar. I also explain how you can ensure that it is ready when you need it.
Why you need a fire extinguisher
To start and grow, a fire needs fuel, oxygen, and heat - elements that abound in General Aviation.
Fires happen before takeoff, in-flight, and after landing.
I’ve heard many hair-raising aviation fire stories over the years.
- A Piper Archer pilot preparing for takeoff, over-primed the engine on a cold day leading to the ignition of pooled fuel.
- An improperly capped terminal lug on the landing gear hydraulic pump of a Cessna 172 caused a horrific in-flight fire. See the re-enactment here: Real Pilot Story: Fire in the Cockpit.
- Worn insulation on electrical wiring caused a short that sparked accumulated dust and grime on a kit plane in flight.
- A compression fitting connecting the brake line to the brake failed on a Cessna 182. When the pilot pressed the brake pedal upon landing, brake fluid squirted onto the hot brake disk causing a fire.
The Aging GA fleet doesn’t help.
What you can do
• Maintain your aircraft
• Get a clean agent fire extinguisher
The next best thing to do is to make sure you have a functioning extinguisher of the correct type and size in your plane and in your hangar.
What type of extinguisher do you need?
There are several things to consider when deciding on a fire extinguisher for your plane.
Is an extinguisher listed on the IPC/Owner’s manual of your aircraft? If it is, you have your answer. Get that one! Often, though, particularly with older aircraft, an extinguisher isn’t listed. Or if listed, the extinguisher may no longer be available. In this case, consider FAA Guidance.
AC20-42D “Hand Fire Extinguishers for Use in Aircraft” and AC120-80 “In-flight fires” are good sources of information. Both recommend the use of “clean agent” fire extinguishers, and against dry chemical/dry powder or CO2.
Dry Chemical extinguishers are effective, inexpensive and readily available. DON’T GET THEM. Their fatal flaw is that they create blinding, choking clouds of corrosive dust. A blinded, choking pilot will be challenged to safely land a plane. If he does, the damage from the dry chemical will be significant.
A Carbon Dioxide extinguisher makes no mess, and the only damage might be to electronic components due to the freezing temperature of the agent as it is discharged. The biggest negative of CO2 is that it is dangerous to use in a confined space. In addition to cooling, CO2 extinguishes fire by removing the oxygen from the air - not good for the pilot.
Having any extinguisher is better than having no extinguisher. But a clean agent extinguisher will safely and effectively put out a fire without causing any mess or damage, and without obscuring the pilot’s vision.
What is a clean agent?
The National Fire Protection Association defines a clean agent as, “any type of fire extinguishing agent that is electrically non-conductive, volatile, or gaseous, and that does not leave a residue upon evaporation.”
Clean agent extinguishers chemically interrupt the combustion process, rather than smothering the fire like dry chemical/dry powder, or by removing the oxygen like CO2.
A note regarding Underwriters Laboratories, fire classes, fire ratings, and clean agents.
• Class A: Common combustibles (wood, paper, rubber)
• Class B: Flammable liquids (fuels, lubricants, solvents)
• Class C: Live electrical
• Class D: Metals (Magnesium, Titanium)
The graphic here identifies the most common classes of fires. “A” is for common combustibles, “B” is for flammable liquids, and “C” indicates that the agent won’t conduct electricity back to the operator. “D” signifies flammable metal fires, and is less common.
The number preceding the fire class letter indicates its relative effectiveness. A 5B:C rated extinguisher is approximately 2.5 times as effective as a 2B:C rated extinguisher.
BEWARE of non-UL listed fire extinguishers! Though illegal in most states, they do exist. Any claims as to the effectiveness of a non-UL listed fire extinguisher are meaningless because the extinguisher has not been tested to a recognized standard. Don’t fall for hairspray bottle type, “fire extinguishing sprays” or other non-standard looking, non-UL listed products. Due to the small size and feeble discharge range, they often require you remain very close to the fire as you wait for the product to discharge completely. A UL listed fire extinguisher is designed to put out a fire from a safe distance in about 10 seconds.
Clean agents are also effective on class A, B, and C class fires - another reason why the FAA recommends them. Note, though, that while a clean agent extinguisher can be used on these classes of fires, the extinguisher itself may be too small to receive an “A” rating. For example, the FAA recommends a 2B:C rating for aircraft with an interior volume of up to 200 cubic feet, and a 5B:C rating for aircraft larger than that.
Clean Agent Benefits Summary
• No corrosive mess
• Does not obscure vision
• Gaseous so it gets around objects
• Does not conduct electricity
AC20-42D Hand Fire Extinguishers for Use in Aircraft
• Interiors > 200 ft3 require a min. 5B:C UL rating
• Interiors < 200 ft3 require a min. 2B:C UL rating
• Agent weight is not relevant
• UL rating is what’s important
Halon – Still the King of Clean Agents
Halon 1211 is the original clean agent. Since the 1970’s, its effectiveness and clean agent properties have made it extremely popular for aviation, military, commercial and even residential use. However, production was banned in 1994 under the Montreal Protocol of Ozone Depleting Substances. Since then, and to this day, new halon fire extinguishers contain recycled halon.
There are three commercially available halon alternatives: Halotron 1, FE-36, and Halotron BrX. The first two have environmental issues of their own, and they are about half as effective, and twice as big and heavy as a like-rated halon extinguisher. They are also more expensive.
The newest halon alternative, Halotron BrX, comes in an extinguisher that is about 30% bigger and heavier than a halon extinguisher. It is also about 5 times as costly.
2B:C Rated Extinguishers: Halon vs. and Halon Alternatives
It is true that halon will eventually be phased out. Current estimates are recharging a halon extinguisher will still be possible well into the 2030s. Given the size, weight and cost advantages over the clean agent halon alternatives, halon fire extinguishers have the most to offer the pilot looking for peace of mind.
Mounting, Inspection, and Maintenance
Whatever extinguisher you choose, you will want to be confident that it will be at hand, and work when you need it to.
The first step is to securely mount the extinguisher where you can reach it. Common locations are under or next to your seat, or on the pilot’s door. If a location is not specified in the owner’s manual, securely mount the extinguisher with its bracket and strong fasteners.
This is where an A&P mechanic is worth their weight in gold. Enlist their help. You will need to do a weight and balance recalculation and obtain field approval by an FAA Designated Airworthiness Representative.
With the extinguisher selected, purchased, and mounted, it is next simply a matter of following the maintenance instructions outlined on the label, and in your extinguisher manual. All fire extinguisher inspection and maintenance follows NFPA code 10.
- When you first install the extinguisher, weigh it and write down the date and gross weight. Extinguishers usually hold their charge for many years unless they have been exposed to extreme conditions or are otherwise damaged.
- Inspect it once a month (or before each flight) to ensure that the pressure gauge reads in the green zone and that the extinguisher has not leaked or been damaged.
Even a securely mounted extinguisher can sustain damage in the confines of a cockpit. Accidentally kicking an extinguisher mounted under a seat happens, and some extinguishers are more easily damaged than others. A pilot once told me that he jumped out of his plane to extinguish a brake fire and the plastic top of his extinguisher came off, rendering it useless! Select an extinguisher that uses metal for key components like the handle, head, bracket, and siphon tube.
- At the annual inspection, it should be weighed and inspected for damage. Compare the weight to the weight noted when you initially installed it. If the weight has dropped below the allowable amount listed on the label, the extinguisher needs to be taken to a fire service company for service.
- Every 6 years, regardless of the gross weight, the extinguisher must be taken to a fire service company for service. At 12 years, this service includes a pressure test of the cylinder.
Practice Makes Perfect
With your extinguisher mounted within reach, and regularly inspected, you can be confident that it will work when you need it to. But will you know how to use it? The instructions are written on the label, but a fire emergency is not the time to read them for the first time!
A first responder told me that even professionals can “go dumb” in an emergency. This is why they place so much emphasis on practice.
Simulate the steps you would take in the event of a fire. Can you quickly remove the extinguisher from the bracket? Imagine aiming the extinguisher at the base of the fire, and squeezing a steady burst of halon to knock it down.
The key word here is “simulate.” Do not actually pull the pin and break the factory tamper seal or you will void the warranty. An unbroken tamper seal is proof that the extinguisher has not been used.
Also, if you actually spray the extinguisher – even just a small amount – the extinguisher will begin to slowly leak.
We recommend you do a practice run every month when you do your inspection. This will ensure you have sufficient muscle memory should a fire emergency occur.
Good news for GA Pilots!
I hope this article inspires pilots to purchase halon fire extinguishers, mount them in their plane and hangar, regularly inspect and maintain them, and practice how to use them so they’ll be ready when needed.
If you have questions about this article, or halon or other clean agent extinguishers, email firstname.lastname@example.org.
About the author
Chris Dieter is Senior Vice President at H3R Aviation, Inc., having joined the Petaluma, California company nearly 20 years ago. During that time he has worked with the FAA, major OEMs, and aircraft parts suppliers to promote aviation fire protection.