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Fire Extinguisher 101

Having a fire extinguisher is crucial to the safety of your business, employees, and customers. It is important that you understand the different types of fire extinguishers as well as the associated components and terminology so you can choose the fire extinguisher that's right for your operation.

Types of Fire

Fires can be fueled by a variety of different materials and, for that reason, are divided into different classes. It is important that you understand these classes so that you can make an educated purchasing decision when selecting your new extinguisher.


Class A Fires

  • Fueled by solid materials such as wood, paper, fabric, and plastics

  • Most common type of fire


Class C Fires

  • Electrical fires involving faulty wiring, electrical equipment, and appliances

  • A danger in breaker rooms, server rooms, and construction sites


Class B Fires

  • Fueled by flammable liquids and gases

  • Can be prominent in gas stations, bars, and chemistry labs


Class K Fires

  • Fueled by grease, cooking oils, and fats

  • Specifically related to foodservice kitchens

Fire Extinguisher Types

Fire extinguishers are uniquely designed to meet the needs of a variety of applications, so it's important to choose the one that's right for you. For example, a different extinguisher may be needed for a commercial kitchen as opposed to a clean room or library. Additional fire extinguisher uses are detailed below.


ABC Fire Extinguishers

  • Fight class A, B, and C fires

  • Filled with Mono Ammonium Phosphate, a corrosive dry chemical agent

  • Must be scrubbed off surfaces once the fire is out


Halotron Fire Extinguishers

  • Fight Class B, C, and sometimes A fires

  • Non-conducting agent evaporates and won't cause static or thermal shock

  • No residue left behind


CO2 Fire Extinguishers

  • Fight class C electrical fires

  • Displace oxygen to suffocate the fire and rob it of its fuel source

  • Not for use in confined spaces


Water-Based Fire Extinguishers

  • Combat Class A fires and sometimes C fires

  • Water serves as the extinguishing agent

  • Often used in libraries, schools, and hospitals


Class K Fire Extiguishers

  • For fires fueled by cooking oils and greases

  • Exclusively used in commercial kitchens

  • Prevents reignition and oils from splashing

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Purple K Fire Extinguishers

  • Fight Class B and C fires; not for use with Class K fires

  • Contain a dry chemical component

  • Effective against flammable liquids as well as electrical fires

Fire Extinguisher Sizes

The size of a fire extinguisher indicates the amount of extinguishing agent it holds and is most often measured in pounds. Sizes can range from as small as 2.5 lb. to as large as 350 lb. While the largest extinguishers will come with built-in wheels to make transportation manageable, size is always important to consider.

What size fire extinguisher does my business need?

Fire extinguisher sizing for your operation will depend on a variety of factors, including...

  • Fire Risks: Be aware of the unique hazards within your operation. The size of a fire that may occur in an office building could be much different than one in a manufacturing plant that specializes in hazardous materials.

  • Room Size and Materials: The size of a room and how it's organized are important as well. A small reception area with limited combustible materials will require a smaller extinguisher than a spacious section of a warehouse that is packed snugly with combustible products.

  • Employee Ability: A fire extinguisher is only as effective as the individual controlling it, so be sure that your employees can handle the one that you choose. A large, high-capacity fire extinguisher might work well for your application, but relying on one that is too heavy or bulky for your workers to use creates a dangerous situation.

Common fire extinguisher sizes and their approximate weight

  • 2-A:10B:C - 4 lb.

  • 3-A:40B:C - 5 lb.

  • 4-A:60B:C - 10 lb.

  • 10-A:80B:C - 20 lb.

Fire Extinguisher Ratings

An ABC Fire Extinguisher might have a UL Rating of 4-A:80-B:C. But what do these fire extinguisher ratings mean? The numbers in the ULC Rating are a relative measurement of how effective a given extinguisher is at fighting certain classes of fires, based on proper fire extinguisher training.

  • A: The number in front of the "A" measures water equivalency. One A is equivalent to 1.25 gallons of water, so a unit with a 4A rating has an equivalent of 5 gallons of water to battle Class A fires.

  • B: The number in front of the "B" is a relative measure of the area an extinguisher can cover.

  • C & K: These letters indicate that an extinguisher can be used effectively against these fire classes.

In practical terms, that means that if Fire Extinguisher 1 has a 4-A:80-B:C rating and Fire Extinguisher 2 has a 1-A:10-B:C rating, Fire Extinguisher 1 is...

  • 4x more potent against Class A fires

  • 8x more potent against Class B fires

  • Both extinguishers can combat class C fires.

What is in a Fire Extinguisher?

Different fire extinguisher types may have some design variations, but they generally feature the same components and operate in similar fashion.

The extinguishing agent comes out of the extinguisher to eliminate fires. It is fed out of the extinguisher's tank via a pickup tube once an expellant (often from a compressed gas canister) is released into the tank. The expellant is released when the safety pin is removed and the discharge lever is squeezed. To aim, users hold the extinguisher by the carrying handle and point the discharge nozzle at the base of a fire. A pressure gauge displays the pressure inside the tank, making it clear if a leak exists or the extinguisher's been used.

What is a Tagged Fire Extinguisher?

Tagged fire extinguishers arrive inspected and tagged so that, in most locales, they can be used immediately upon delivery. They have been tested to ensure that they operate properly and display tags that are valid for 12 months from the date of inspection per the NFPA-10 code. Before purchasing a tagged extinguisher, check your local fire inspection codes to make sure it won't need to be re-tagged to meet the specific guidelines of your Province.

Provincially-mandated rules and regulations require untagged fire extinguishers be inspected and tagged before it can be used. Purchasing an untagged extinguisher means it will be inspected on-site at your business, which assures you that your unit is in compliance with the codes in your area and you know exactly when your tags expire. The downside is that your extinguisher cannot be used as soon as it arrives.


What is the Difference Between a Rechargeable and Non-Rechargeable Fire Extinguisher?

  • Rechargeable fire extinguishers are built to be reused. Note that when a rechargeable fire extinguisher is used, it needs to be recharged before going back into service. Fire extinguishers can be recharged by contacting a trained technician at a fire extinguisher servicing company.

  • Non-rechargeable fire extinguishers are often less expensive, but built in a manner that allows them to be used only once. Even if only partially discharged, a non-rechargeable fire extinguisher must be replaced after it is used.​


*Each type of extinguisher must be serviced whenever its seal is broken for any reason (like usage, aging, and tampering). Additionally, a certified company or AHJ (Authority Having Jurisdiction) must service the unit annually.

Fire Extinguisher Pressurization

Extinguishers must be pressurized for extinguishing agents to travel up the pickup tube and out of the discharge nozzle. This pressure is administered by an expellant source (normally a gas cylinder) in a few different ways.


Stored Pressure

The extinguishing agent and expellant source are contained within the same cylinder. They are typically the most affordable option upfront with lower service costs and instant activation.

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Pressure Transfer

The extinguishing agent and expellant source are contained in separate cylinders, allowing for larger agent capacities than stored pressure models. The agent cylinder doesn't have to be depressurized when replacing the agent, as is necessary in stored pressure units. In pressure transfer extinguishers, pressure is at its peak when initially activated and decreases throughout the discharge process.

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Pressure Regulated

Offering the same benefits as pressure transfer extinguishers, pressure regulated units feature an extinguishing agent and expellant source within separate cylinders. These models come with a pressure regulator to maintain smooth, consistent discharge throughout the discharge process. Because the regulator delivers consistent pressure from start to finish, a larger expellant cylinder is required than with pressure transfer units.

Fire Extinguisher Accessories

Make sure that your fire extinguisher is secure, easily accessible, and clearly labeled with brackets, signs, and other helpful accessories.


Fire Extinguisher Brackets

  • Keep extinguishers secure but easily accessible

  • Vehicle brackets secure extinguishers through bumps and vibration


Fire Extinguisher Cabinets

  • Cabinets enclose extinguishers for tamper-resistance

  • Clear covers maximize visibility


Fire Extinguisher Signs and Labels

  • Promote quick identification

  • Use eye-catching, vibrant red and white coloring

Fire Extinguisher Frequently Asked Questions

How long do fire extinguishers last?

Fire extinguishers are generally warranted for somewhere between 5 - 15 years, but be sure to review your model's warranty for specific information.

Where do you recharge fire extinguishers?

Whether needed as part of regular maintenance or immediately after use, your extinguisher should be recharged by a trained professional from a fire protection company.

How do you dispose of fire extinguishers?

We discharge the powder in a closed loop system to ensure all of it is captured and disposed of. We then take the extinguisher apart and drill a hole in the unpressurized cylinder to ensure it cannot be used again in the future. 

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