Does anyone know how class "F" fire extinguishers work?

How do class “F” fire extinguishers work? Has anyone here ever used one? For anyone who doesn’t know what these are, they are another type of fire extinguisher that few have heard of and they are for class F fires, another type of fire in addition to class A, B, C, D, and E, fires. A class F fire is a fire caused by oils or fats.

Also, why is this section of the forum so empty?!?

I assume you are talking about class “K” extinguishers? I’ve never heard of class “F”. But a class K extinguisher is used in conjunction with a commercial kitchen extinguishing systems like Ansul as additional or backup for the fixed system. It should be compatible with the agent used in the fixed system. Because of the oils used in commercial kitchens burn hotter than oils used years ago, they had to develop the new standards. A typical ABC or BC type will not work to put out these newer grease fires. Class K uses a foam - if you pick one up you can hear the chemical sloshing around inside. They also have to be mounted at the manual activation station for the kitchen hood system and have a sign mounted at the extinguisher saying to use it AFTER the fixed system. I believe the basic idea is if there was an obstruction from the discharge of the fixed system, you could use the portable extinguisher to deal with that.

Class “K” extinguishers sometimes have a long stick with a nozzle on the end as well so you can spray it straight down onto the fire.

So yeah, there is no Class F, G, H, I, or J.

Also fun fact, a “PKP” extinguisher, despite how it sounds (Purple K Powder) is not a Class K extinguisher. It’s actually a Class B & C extinguisher.

I think it might have actually been a class K, not F. On the website I heard about it on, it did show a picture of one and it did have a really long nozzle.

Very true, no Class “F” Extinguisher here in the U.S. that is, and most likely you are referring to a Class “K” which is used mainly for commercial kitchen use.

This was required when we switched our cooking oils from animal fat based oils, to the hotter cooking temperature vegetable oils. Vegetable oils that will re-ignite when a conventional ABC, and usually BC powder (Class “B”) was used. The old powder would coat initially, but the still boiling oil would break the powder apart, exposing the hot oil again to air, and the oil being at, or above its auto ignition temp, will re-ignite. Many a restaurant burned down due to this until the BC Extinguisher and hood systems were switched out to the Class “K” wet Agent systems.

The class “K” gels when it is applied to the flaming oil, coats and stays locked to cool and smother, the other term in fire suppressants of this type is the action of saponification. Below is a very good explanation from Wikipedia. But an interesting side note is the term “F” not “K” is used outside of the U.S.

“Fire extinguishers -
Fires involving cooking fats and oils (classified as class K (US) or F (Australia/Europe/Asia)) burn hotter than flammable liquids, rendering a standard class B extinguisher ineffective. Flammable liquids have flash points under 37 degrees Celsius. Cooking oil is a combustible liquid, since it has a flash point over 37 degrees Celsius. Such fires should be extinguished with a wet chemical extinguisher. Extinguishers of this type are designed to extinguish cooking fats and oils through saponification. The extinguishing agent rapidly converts the burning substance to a non-combustible soap. This process is endothermic, meaning that it absorbs thermal energy from its surroundings, which decreases the temperature of the surroundings, further inhibiting the fire.”

Ref: Saponification - Wikipedia

There is even a Water Mist fire extinguisher that has a Class “C” rating that can be used on energized electrical equipment up to 100Kv! and uses a special spray nozzle and Deionized water to do so. I think I’ll turn off the power first, and then it moves from a Class “C” to a Class “A” fire unless oils are involved Class “B”, in which an ABC extinguisher is used.

This is from my (2013) NFPA 10 Standard for Portable Fire Extinguishers, Chapter 5:

Chapter 5 Selection of Portable Fire Extinguishers

5.1 General Requirements. The selection of fire extinguishers
for a given situation shall be determined by the applicable
requirements of Sections 5.2 through 5.6 and the following
(1) Type of fire most likely to occur
(2) Size of fire most likely to occur
(3) Hazards in the area where the fire is most likely to occur
(4) Energized electrical equipment in the vicinity of the fire
(5) Ambient temperature conditions
(6) Other factors (See Section H.2.)

5.1.1 Portable fire extinguishers shall be installed as a first
line of defense to cope with fires of limited size, except as
required by 5.5.5.

5.1.2 The selection of extinguishers shall be independent of
whether the building is equipped with automatic sprinklers,
standpipe and hose, or other fixed protection equipment.

5.2 Classifications of Fires. Fires shall be classified in accordance
with the guidelines specified in 5.2.1 through 5.2.5.

5.2.1 Class A Fires. Class A fires are fires in ordinary combustible
materials, such as wood, cloth, paper, rubber, and many

5.2.2 Class B Fires. Class B fires are fires in flammable liquids,
combustible liquids, petroleum greases, tars, oils, oil-based
paints, solvents, lacquers, alcohols, and flammable gases.

5.2.3 Class C Fires. Class C fires are fires that involve energized
electrical equipment.

5.2.4 Class D Fires. Class D fires are fires in combustible metals,
such as magnesium, titanium, zirconium, sodium, lithium,
and potassium.

5.2.5 Class K Fires. Class K fires are fires in cooking appliances
that involve combustible cooking media (vegetable or
animal oils and fats).

I hope that helps,

Was this section of the forums ever erased?

It was only created in July I think, hasn’t generated a lot of topics yet. Have an interest in suppression systems?

Not really surpression systems. I just had a question on class k fire extinguishers and also thought I would be the fifth contributor to the suppression forum.

The funny thing is that I was the one who suggested this section and it came true. (A Wish LOL:D) Anyway I have been wanting to upload many content up on this section but still have been SoOoO busy with work and school :cry: