Fire is a dangerous hazard on aircraft, and having an appropriate fire extinguisher is crucial to mitigate the risks. Not all types are suitable for the aviation environment.

The FAA (Federal Aviation Administration) recommends that aircraft be equipped with Halon or Halon replacement fire extinguishers. For large aircraft, the minimum rating is 5B:C, for small aircraft it is 2B:C. To find out more about these ratings, the types of extinguishers, and which extinguishers meet aircraft fire extinguisher requirements, see below.

Types of Fire

Underwriters Laboratories has created a class and rating system for fires, which allows us to see what type and size of fire a UL-listed extinguisher is rated for. Not only this, a UL listing ensures an extinguisher has undergone extensive testing to verify its effectiveness.

Note: The FAA does not provide a list of authorized fire extinguishers for aircraft. The FAA does specify the following regulations. According to AC 20-42D, "Hand Fire Extinguishers for Use in Aircraft:"
"The FAA accepts hand fire extinguishers approved by Underwriters Laboratories, Inc."


There are five types of fires, and they are divided into the following classes:

• Class A: Ordinary combustibles. These fires involve ordinary combustibles such as paper, wood, and cloth.
• Class B: Flammable liquids. These fires involve flammable liquids, gases, and greases such as gasoline, oil, and propane.
• Class C: Electrical. Any fire involving electrical equipment such as wiring, fuse boxes, and electrical motors. Class C fire extinguishers contain a non-conductive agent that is safe to use on live electrical equipment.
• Class D: Flammable metals. This includes metals such as magnesium, titanium, and potassium.
• Class K: Fire Extinguishers: This type of extinguisher is designed to combat fires that involve cooking oils and fats such as those found in commercial kitchens. Class K fire extinguishers contain a wet chemical agent that reacts with the oil or fat, creating a soapy foam that extinguishes the fire.

The primary types of fire that occur in aviation are most often class B, or C.

Fire Extinguishers

There are many types of extinguishers on the market, but not all are suitable for aviation fire safety. Let’s look at each type as well as the pros and cons, and if they are suitable for aviation fire fighting.

Water extinguishers
Pros: Suitable for Class A fires that involve paper, wood, cloth, and other common combustibles. They work by cooling the fire and removing its heat.
Cons: These are not suitable for class C fires.
Suitable for aviation: No


Foam extinguishers
Pros: Suitable for Class A and B fires that involve flammable liquids like gasoline, oil, and paint. They work by smothering the fire and preventing the release of flammable vapors.
Cons: Not suitable for class C fires and can cause damage. There is a lot of clean up and it can leave a residue.
Suitable for aviation: No

Carbon dioxide (CO2) extinguishers
Pros: Suitable for Class B and C fires that involve flammable liquids and electrical equipment. They work by removing oxygen from the fire and cooling it down.
Cons: These are dangerous to use in enclosed, occupied spaces. CO2 displaces oxygen, which can lead to asphyxiation if there isn’t enough ventilation. It can also cold shock electronic systems.
Suitable for aviation: No


Dry chemical extinguishers
Pros: Suitable for Class A, B, and C fires that involve flammable liquids, electrical equipment, and combustibles. They work by smothering the fire and interrupting the chemical reaction that sustains it.
Cons: It will make a corrosive mess, and impair vision.
Suitable for aviation: No, in fact the FAA has recommended against it.


Wet chemical extinguishers
Pros: Suitable for Class F fires that involve cooking oils and fats. They work by cooling the fire and creating a barrier between the fuel and the oxygen.
Cons: Not rated for class A, B, or C fires.
Suitable for aviation: No

Clean agent extinguishers
Pros: Suitable for Class A, B, and C fires that involve sensitive equipment like computers, servers, and telecommunications gear. They work by removing heat and interrupting the chemical reaction that sustains the fire.
Cons: Though all halon-alternative clean agents are rated for A-class fires, extinguishers don’t get an A rating until they contain approximately 11+ lb. of agent. Halon is an ozone-depleting substance and is scheduled for eventual phase-out, though we expect new Halon extinguishers to be available for several more years. Furthermore, the eventual phase out will not affect extinguishers already in use.
Suitable for aviation: Yes

Choosing the Right Fire Extinguisher for Your Aircraft

The available aviation fire extinguisher options vary in size, weight, and effectiveness. Of all the clean agents available that meet aviation fire extinguisher requirements, Halon is the most effective pound-for-pound. However, due to the environmental concerns related to Halon, newer alternatives have been made available.

Per AC 20-42D the minimum requirement for small airplanes or rotorcraft is 2B:C. Using this as a baseline we can compare the effectiveness and size of aviation fire extinguisher types:

Agent	Agent Weight	Rating	Cost	Availability
Halon	1.25 lb.	2B:C	$294	Available
Halotron 1	2.5 lb.	2B:C	$298	Available
Halotron BrX	1.92 lb.	2B:C	$1,378	Available
FM-200	2.75 lb.	2B:C	$283	No longer available
FE-36	2.5 lb.	2B:C	$400 - $800	Limited availability

Given the size and weight limitations of an aircraft, we expect Halon to remain the most popular option until its eventual phase-out. Halotron BrX is the closest in size and effectiveness of all the Halon replacements and some aircraft manufacturers are already making the transition.



If you would like to learn more about the guidance the FAA has issued for extinguishers you can review AC 20-42D here.