How to Use a Fire Extinguisher

Fire extinguishers are used across the globe on a daily basis to put out fires and save structures from destruction. Since the first extinguisher was patented in England in 1723, extinguishers have allowed bystanders to stop fires before they could get out of control.

There have been many different designs, from exploding models using gunpowder and fuses, to fully automated hood systems in modern kitchens, to the common handheld extinguishers you see in public buildings. Extinguishers are everywhere and can save the day if they become needed.

However, there is a right way and wrong way to use a fire extinguisher. There are also several varieties of extinguisher, and they all have different purposes. We are going to talk about the different kinds and their intended purposes as well about how to use one properly. We will also discuss if you need an extinguisher as part of your preps, and if so, which one should you buy.

the fire triangle

By Gustavb – Self-published work by Gustavb, CC BY-SA 3.0, Link

The Fire Triangle

To understand how fire extinguishers work we first need to know how fire itself works. Fire is a chemical reaction that occurs when three factors are present. The three components each make up a side of the triangle, and when all are present, a fire will sustain itself until one of the three parts is removed. This is what fire extinguishers do, is remove one of the components of combustion, stopping the fire. These three components are Fuel, Oxygen, and Heat.

Fuel is what is being burned. It can be gasses, solids, liquids, and everything in between. Something combustible has to be present for a fire to sustain itself.

Oxygen is one of the components, and it has to be present for combustion to occur. Of course, oxygen is in the air we breathe so most locations on the planet will have available oxygen. Contrary to popular belief, oxygen is not flammable. However, since it is an element of combustion, when a fire hits an oxygen-rich environment it will grow so fast and so large that it seems to explode.

Heat is the last component. Heat is the match, spark, or even fire that touches off the combustion. Heat sources can come from all kinds of sources and do not have to be very large to get combustion going if the other components are present.


Classes of Fire

Fire extinguishers are classified by the type of fire that they will extinguish. Fire is broken down into five categories, “A”, “B”, “C”, “D”, and “K”. Each category is defined by the type of material that is on fire, and each requires a different kind of extinguishing agent.

class a fire symbol


Class A is used for ordinary combustibles, such as paper, wood, some plastics, and textiles. This class of fire requires the heat-absorbing effects of water or the coating effects of certain dry chemicals in order to extinguish the fire.  Extinguishers suitable for Class A fires are identified by a triangle containing the letter “A.” One way to remember this category is to associate “A” with “ash”, many of the combustibles that are covered by the “A” category are ones that would create ashes.

class b fires


Class B is for flammable liquid and gas fires such as oil, grease, gasoline, etc. These fires require extinguishers to deprive the fire of oxygen breaking the fire triangle by inhibiting the release of combustible vapors. Extinguishers that are suitable for Class B fires will be identified by a square containing the letter “B.” One way to remember this category is to associate “B” with “big” or “bad”, this is due to the fact that B class involves burning fuel sources, and can be some of the most dangerous fires.

class c fires


Class C is for fires that involve live electrical equipment, which requires the use of electrically nonconductive extinguishing agents. These extinguishers break the fire triangle by removing the oxygen in the area of the fire. (Once the electrical equipment is de-energized, extinguishers for Class A or B fires may be used.) Extinguishers that are suitable for Class C fires will be identified by a circle containing the letter “C.” One way to remember this class is to associate “C” with computer equipment.

class d fires


Class D is for combustible metals, such as magnesium, titanium, sodium, etc., which require an extinguishing medium that does not react with the burning metal. These are specialized extinguishers and will only be in places where combustible metals are known to exist, such as industrial areas that work with the metals. Extinguishers that are suitable for Class D fires will be identified by a five-point star containing the letter “D.”

class k fires


Class K is for fires involving cooking mediums such as fats, grease, and oils in commercial cooking sites such as restaurants. These fire extinguishers use saponification to break the fire triangle and extinguish the fire.

Saponification takes place when alkaline mixtures, such as potassium acetate, potassium citrate, or potassium carbonate, are applied to burning cooking oil or fat. The alkaline mixture combined with the fatty acid creates a soapy foam on the surface that holds in the vapors and steam and extinguishes the fire. Class K extinguishers can be identified by the letter K. To remember this class, you can associate it with “kitchen”.

fire fighting

Types of Extinguishers

We discussed the different classes of fire, so now we are going to talk about the different kinds of extinguishers. While all fire will fall into one of the five classes, extinguishers can be rated to work of multiple different classes of fire based on the type and the extinguishing agent. Therefore instead of having an “A” extinguisher and a “B” extinguisher, you could have an “AB” extinguisher that would be appropriate for either “A” or “B” class fires.

There are also many different styles of extinguishers. We usually think about the handheld cans that you spray towards a fire. However, there are automatic extinguishers that fill a room with extinguishing agents or hood systems that activate when a certain temperature is detected, extinguishers come in many shapes and sizes. For the rest of this article, we are going to focus on the handheld variety which is called portable fire extinguishers.


Water – Air-pressurized Water Extinguishers (APW)

These extinguishers are filled with plain water and pressurized. Some of them also have a detergent added to the water that will create foam. They are easy to recognize by their large silver containers. They stand about two to three feet tall and weigh approximately 25 pounds when full. These extinguishers are for class “A” fires only.


CO2 or Dry Chemical – Carbon Dioxide Extinguishers

This type of extinguisher is filled with Carbon Dioxide (CO2), a non-flammable gas under extreme pressure. These extinguishers work by displacing oxygen or taking away the oxygen element of the fire triangle.

Because of its high pressure, when you use this extinguisher pieces of dry ice shoot from the horn, which also has a cooling effect on the fire. These extinguishers are meant for class “B” and “C” fires. These extinguishers will have a red cylinder and can range from 5 to 100 pounds.


dry chemical fire extinguisher

Multi-purpose – Dry Chemical Extinguishers

Dry chemical extinguishers put out fires by coating the fuel with a thin layer of fire retardant powder. This separates the fuel from the oxygen and breaks the fire triangle. Dry chemical extinguishers are usually rated for Class “A”, “B”, and “C” fires. They use a compressed, non-flammable gas as a propellant to propel the extinguishing agent. ABC fire extinguishers are red in color, and range in size from five pounds to 20 pounds.

These extinguishers are the most common and are what you are likely to find in public hallways, shopping centers, offices, mechanical rooms, schools, and many other buildings. These are also the type that is best suited for most homes.


class- k fire extinguisher

D & K Extinguishers

Class “D” and “K” extinguishers, while being their own class, are designed based on the dry chemical extinguishers, or the design of the air-pressurized water extinguishers. What makes these extinguishers different is the extinguishing agent.


How to use a Portable Fire Extinguisher

To use a portable fire extinguisher you will need to follow some steps to have the greatest effect on the fire. To teach this procedure, you will use the acronym PASS.

Pull – Aim – Squeeze – Sweep


First, you will need to locate and extinguisher and make sure that it is the correct type for the fire conditions. Then you will need to pull the silver pin, located just under the handle on top of the extinguisher. This pin acts as a safety device to prevent accidental activation of the extinguisher.




Once you have the nozzle aimed at the base of the fire, squeeze down on the handle to actuate the extinguisher and begin to spray the extinguishing agent. You do not have to worry about the nozzle spraying out of your hands or the force knocking you backward. Even large extinguishers will not have that kind of pressure.


Once you activate the extinguisher, you want to slowly sweep the nozzle back and forth across the fire, to ensure you cover as much of the fuel source as you can. Remember that when you initially spray the fire, you will see a dramatic drop in the flames, but that does not mean the fire is fully out. Make sure you continue spraying until no flame is visible. Once the fire is all the way out, make sure you standby with the extinguisher, or a new one if possible, in case the fire flares back up.

fire extinguisher pass

Should you have a fire extinguisher as part of your preps?

In my opinion, you should have several. We all know that when SHTF one of the first things that are going to drop out is municipal services. They all have families at home as well, and whatever they are being paid is not going to be worth the total chaos.

So if there is no fire department coming, what would you do if you had a small fire? Could you imagine losing your entire home, with all your preps in it?

I have multiple fire extinguishers in different spots throughout our house. I also have spares for most of them, in case we have to use one. You can buy this Kidde Dry Chemical ABC on Amazon. We buy two per year and switch them around as we see fit. Over the last several years, our $80 investment has given us a decent amount of fire extinguishing ability in case we need it.

Where to Keep Fire Extinguishers

  • near the bed
  • a larger one in the garage
  • in the kitchen
  • near stoves but not too close
  • near the front door, on the side with the door knob, so you can quickly grab it whether you’re rushing in or out
  • in the proximity of other fire hazards but not too close, and keep in mind the more visible they are, the better

Now fire extinguishers are not going to put out a huge fire. If it is more than a trash can or the countertop, there is a very low probability of getting the fire out. The way extinguishers work is by interrupting the fire triangle, and that typically only happens for so long. If you are spraying the left side of the room, when you go to spray the right side oxygen can creep back over, and the left will start burning again.

However, I feel that it is at least worth the chance. As long as you are not standing in heavy smoke, and you can safely spray the extinguisher then I think it’s worth the try.

Another place that a lot of people never think to put an extinguisher is in your vehicle. A 2.5lb cylinder under the driver’s seat can be the difference between some wires on fire and replacing a vehicle. I personally have used the extinguisher in my truck twice in the last ten years or so, both helping other people involved in a crash.

Extinguishers are not the answer to all fire concerns, but they are beneficial to have around when the time comes that you need one. With the low cost and ease of mounting, it easy to have a few around just in case.

fire extinguisher pinterest

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About Steve Hensley

Steve Hensley
Born and raised in Kentucky, Steve grew up deep in the mountains on a family farm. After college, Steve spent over 15 years working in public service and has experience in Fire, EMS, and Law Enforcement. He has also worked with training and deploying search & rescue and service dogs for utilization in a variety of services. Steve is also a Scout Leader with the Boy Scouts of America, and works to teach preparedness to the next generation. Steve has worked with and taught firearms and self-defense in multiple venues, from tactical applications to long range shooting, and also has extensive training in first aid and wilderness first aid. An active prepper, Steve has devoted hundreds of hours to mastering and teaching skills and techniques for use in survival, homesteading, and general preparedness.

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