Fire Extinguisher Guide

Fire Extinguisher Guide

Fire extinguishers are a necessary safety item that should be in every home and business. The following guide is designed to help you determine how many, what size, and what type you need. It will also discuss the different classes and types of extinguishers and their uses.


Fire extinguishers are rated by Underwriter’s Laboratories, Inc. according to the types of fires they are designed to put out. There are three classes of fires. Class A fires involve paper, wood, cloth, rubber, and some plastics. Class B fires involve flammable liquids, such as gasoline, paint thinner, grease, motor oil, and solvents. Class C fires are electrical in nature. As a rule, fire extinguishers rated A, B, and C are best for home use.

All fire extinguishers also receive a numeric rating that indicates the size of the fire a particular unit is capable of fighting. For example, a 4-A rating means that the unit will put out twice as much Class A fire as a unit with a 2-A rating. There are no numeric ratings for C class (electrical) fires, because the C rating simply means that the extinguishing agent in the unit is not electrically conductive.

Check the dial gauge on your fire extinguisher monthly. The needle on the gauge indicates whether the unit is operable or in need of recharging. When required, have the unit recharged by a qualified professional–you can usually find these professionals listed under Fire Extinguishers in your Yellow Pages. Recharging is required after every use, no matter how brief.

Handled correctly, even a small 5 lb. dry chemical extinguisher can put out a fairly large fire. View this video for a demonstration.


Fire Extinguisher Classes/Ratings

The following symbols and/or letters should be visible on the fire extinguisher label. They indicate which type of fire the extinguisher should be used on. All new fire extinguishers will use the larger symbols below as opposed to the previous style (a letter in a colored shape) shown next to each class name. Class A – Ordinary Combustibles (Wood, Paper, Cloth, etc.) Previously: Class A Symbol

Class A Symbol
Fires whose fuel is paper, wood, cloth or other ordinary combustibles (not liquid, electric, or metallic) would be classified as an ‘A’ fire. Most fires we encounter are class ‘A’ fires. Since they are the most common, the majority of fire extinguishers can extinguish a class ‘A’ fire. Class ‘A’ fires can either be smothered or drowned to extinguish them. Look for an extinguisher with the symbol to the left if you need to extinguish a class ‘A’ fire.

Class B – Burning Liquids/Gases (Gasoline, Cooking Fats, Oils, etc.) Previously: Class B Symbol

Class B Symbol
Fires fueled by liquid (not ordinary, electric, or metallic) combustibles like gasoline, kerosene, propane, cooking fats, and oils would be classified as a ‘B’ fire. To extinguish a class ‘B’ fire, either physical or chemical smothering must occur. DO NOT throw water on a class ‘B’ fire as it will not extinguish the fire and often will cause the burning liquid to splash. Look for an extinguisher with the symbol to the left if you need to extinguish a class ‘B’ fire.

Class C – Live Electrical Equipment (Motors, Appliances, Switches, etc.) Previously: Class C Symbol

Class C Symbol
Fires ignited by live electrical equipment (not ordinary, liquid, or metallic) such as computers, appliances, and switches are classified as a ‘C’ fire. Class ‘C’ fires must be smothered. NEVER use water or other liquids that might serve as a conductor for electricity. Look for an extinguisher with the symbol to the left if you need to extinguish a class ‘C’ fire.

Class D – Combustible Metals (Magnesium, Lithium, etc.) Previously: Same as below. 

Class D Symbol
Fires fueled by combustible metals like magnesium and lithium (not ordinary, liquid or electrical) are different enough to receive their own classification, class ‘D’. Look for an extinguisher with the symbol to the left if you need to extinguish a class ‘D’ fire.

Class K – Cooking Materials (Cooking oils/fats/grease) Previously: Class K Symbol

Class K Symbol
This is a newer classification of fire. Class ‘K’ extinguishers are specifically designed to supplement fire suppression systems in kitchens. These extinguishers are designed for cooking oil, fat, and grease fires. Look for the letter ‘K’ symbol or the symbol to the left if you need to extinguish a class ‘K’ fire.
Multi-Class – Combinations of the classes above. 
No Symbol Available. What if your fire is gasoline (class B) soaked rags (Class A) or what if you have a live electric wire (class C) igniting magnesium (class D). Many scenarios exist for multi-class fires to exist. Which fire extinguisher should you use? Is it necessary to maintain five different extinguishers? You can, but it is not necessary. The majority of extinguishers can take care of multiple classes of fires. Most common extinguishers can handle A, B, and C class fires but remember to always check the label first before use. Class ‘D’ and Class ‘K’ are for less common applications and are not likely to be combined with other fire extinguisher classes.
Fire Extinguisher Types (extinguishing agents)
There are eight different extinguishing agents used in fire extinguishers. They consist of ABC Dry Chemical, BC Dry Chemical, Dry Powder, Water, Foam, Wet Chemical, Halogenated, and Carbon Dioxide. As shown below, each of these agents apply to one or more of the fire classes mentioned above.
ABC Dry Chemical – Works on class A, B, and C fires (Multipurpose).
Class A Symbol
Class B Symbol
Class C Symbol
BC Dry Chemical – Works on class B and C fires.
Class BSymbol
Class C Symbol
Carbon Dioxide – Works on class B and C fires.
Class B Symbol Class C Symbol
Water – Works on class A fires.
Class A Symbol
Foam – Works on class A and B fires.
Class A Symbol Class B Symbol
Halogenated* – Works on class A, B, and C fires.
Class A Symbol Class B Symbol Class C Symbol
Dry Powder – Works on class D fires.
Class D Symbol
Wet Chemical – Works on class K fires.
Class K Symbol

* Halogenated extinguishers are recommended for use around sensitive electrical equipment due to the fact that they will not leave a possibly damaging residue on the equipment as will other extinguishing agents.


Fire Extinguisher Recommendations

The following common types and sizes of fire extinguishers will handle the majority of fire risks found in most commercial, industrial and home environments.


Photo - Extinguishers Multipurpose Dry Chemical ABC Extinguisher – Minimum Size (5 lbs.)
Class A SymbolClass B SymbolClass C Symbol

Multipurpose dry chemical extinguishers will handle most types of fires that occur in your home. They come in a variety of common sizes from 1 1/2 lbs. to 20 lbs. Generally we recommend a 5 lb. extinguisher for home use. It’s big enough to put out most small fires and not to heavy enough to be awkward.

Photo - Extinguishers Dry Chemical Stored Pressure Extinguishers – Various Sizes
Class B SymbolClass C Symbol

Dry Chemical Stored Pressure Extinguishers are designed to meet the specific needs of industrial and commercial occupancies where there is a flammable liquid or special hazard risk. They generally range in size from 5 lb. up to 150 lb. cart-mounted extinguishers. They can cover a variety of hazard classes, but are generally used for class B (flammable liquids) and C (electrical) fires.

Photo - Extinguishers Class K Fire Extinguisher – 2 1/2 gallons
Class K Symbol

Class K extinguishers are designed for commercial restaurant applications and are generally contain 2 1/2 gallons of extinguishing agent. They are compatible with hood and duct fixed extinguishing systems.

Fire Extinguisher Use

How to Use a Fire Extinguisher (Select images for a closer view)

Even though extinguishers come in a number of shapes and sizes, they all operate in a similar manner. Here’s an easy acronym for fire extinguisher use:

P A S S — Pull, Aim, Squeeze, and Sweep

Graphic - Pull Pull the pin at the top of the extinguisher that keeps the handle from being accidentally pressed.
Graphic - Aim Aim the nozzle toward the base of the fire. Stand about 8 feet from the fire.
Graphic - Squeeze Squeeze the handle to discharge the extinguisher. If you release the handle, the discharge will stop.
Graphic - Sweep Sweep the nozzle back and forth at the base of the fire. After the fire appears to be out, watch it carefully since it may re-ignite!

Whenever possible, use the “Buddy System” to have someone back you up when using a fire extinguisher. If you have any doubt about your personal safety, or if you can not extinguish a fire, leave immediately and close off the area (close the doors, but DO NOT lock them). Leave the building but contact a firefighter to relay whatever information you have about the fire.

Do not walk on an area that you have “extinguished” in case the fire reignites or the extinguisher runs out! Remember: you usually can’t expect more than 10 full seconds of extinguishing power on a typical unit and this could be significantly less if the extinguisher was not properly maintained or partially discharged.

Recharge any discharged extinguisher immediately after use. If you discharge an extinguisher (even just a tiny bit) or pull the pin for any reason, call your campus or corporate Fire Marshal’s office to arrange a replacement.

Do Not Fight the Fire Unless ALL of the following apply:

  1. Everyone else is out of the building
  2. The building is being evacuated (fire alarm is pulled)
  3. The fire department is being called (dial 911).
  4. The fire is small, contained and not spreading beyond its starting point.
  5. The exit is clear, there is no imminent peril and you can fight the fire with your back to the exit.
  6. You can stay low and avoid smoke.
  7. The proper extinguisher is immediately at hand.
  8. You have read the instructions and know how to use the extinguisher.