The ABCs and 123s Of Fire Extinguisher Ratings

Angela Brown
Written by Angela Brown
Updated July 9, 2021
Fire extinguisher handle
Nuroon Jampaklai / EyeEm/EyeEm via Getty Images

The numbers and letters on your fire extinguisher identify what the extinguisher is designed to handle

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Having a fire extinguisher in your home, garage, and shop can make the difference between a minor mishap and an emergency. However, you shouldn’t just grab the first fire extinguisher you see at the store. You’ll want to do a bit of pre-buying detective work to make sure you purchase one with the correct fire extinguisher rating for your needs.

Not All Fire Extinguishers Are Created Equal

Most buyers don’t know that there are eight different types of fire extinguishers. For example, certain extinguishers are specifically designed to handle fires in your house or garage, while others are designed for areas with dangerous chemicals. Using the wrong type of extinguisher can be dangerous. For example, using a powder-based extinguisher shouldn’t be used indoors as it can cause breathing problems. Alternatively, if you use an extinguisher not designed for electrical fires, you risk being electrocuted. To keep your home and family safe, purchase a fire extinguisher with the correct rating.

Types of Fire Extinguishers

Fire extinguishers act differently based on the ingredients and canister. Some are more suited for harsher conditions (like storage in a freezing climate), while others are specifically designed to create a barrier between oxygen and fuel elements, or protect against potential contamination from chemicals. 

The most common types of fire extinguishers include:

1. Carbon Dioxide Extinguisher: Suited for electrical fires and flammable liquids. This extinguisher uses CO2 to suffocate the fire.

2. ABC Powder Fire Extinguisher: This extinguisher is multipurpose and uses a fine chemical powder to blanket the fire and remove oxygen. The powder doesn’t conduct electricity, so it’s safe to use on electrical fires. This extinguisher is suitable for most homes. 

3. Wet Chemical Fire Extinguisher: This fire extinguisher is ideal for Class K fires involving animal and vegetable fats. This extinguisher uses mist to cool the fire and then covers the area with a solution to prevent fires from reigniting.

4. Water Mist Fire Extinguisher: This extinguisher works on most fire classes by releasing tiny water molecules to suffocate the fire and cool temperatures. The water in this fire is safe to use on electrical fires. 

5. Foam Fire Extinguisher: The foam in this extinguisher works best on class A and B fires, but it’s not suitable for gaseous fires. The foam blankets the fire, which prevents vapors from rising and cools the surface. 

6. Clean Agent Fire Extinguisher: This fire extinguisher is best suited for Class B and C fires. The liquid in the extinguisher turns to gas when it hits the air. It’s safe for use around animals and people and leaves no residue.

Fire Extinguisher Classes

All fire extinguishers receive a rating from the Underwriters Laboratory (UL). The lab tests each extinguisher for safety and labels them according to their ideal use. Each extinguisher will have a letter and number.

Each extinguisher receives a letter classification to identify the type of fires it’s designed to put out:

  • Class A extinguishes fires on typical combustibles like wood, plastic, or paper

  • Class B extinguishes flammable liquids like gas and oil

  • Class C extinguishes electrical fires

  • Class D extinguishes fire involving metal

  • Class K extinguishes typical kitchen fires involving oil and grease

Class A, B, and C are ideal for the typical home. Class D and K are better suited for restaurants, manufacturing facilities, or your garage if it doubles as a workshop. 

Homeowners should look for an ABC extinguisher. An ABC extinguisher uses a fine powder to suffocate a fire and prevent reignition. This extinguisher will put out the most common home fires and is safe to use on electrical fires.

The National Fire Protection Association recommends only attempting to put out fires in a small, confined area. If the fire is growing, your priority should be to get everyone away from the fire and call 911. 

Fire extinguisher on blue wall
Chakrapong Worathat / EyeEm/EyeEm via Getty Images

Fire Extinguisher Number Ratings

In addition to letter classification, each extinguisher has a number rating. For example, if you look at the UL inspection label, you might see the Classification: 4-A; 80B; C.

The letters (A, B, and C) indicate which fires this extinguisher can handle. In this case, fires containing wood, plastic, paper, gas, and oil, as well as electrical fires. 

For the A-rating, the number indicates the water equivalency of the powder in the extinguisher. In our example above, the 4 represents 5 gallons. A 2 on the label would indicate an equivalent of 2.5 gallons of water. 

For B fires, which are more likely to spread (since they have liquid components), the number indicates how much square footage the extinguisher can cover. In this example, the 80 indicates 80-square feet if the user sweeps the extinguisher side-to-side.

Will My Fire Extinguisher Expire?

Most fire extinguishers won’t have an expiration date listed. However, most last between 10 to 12 years. Check the manufacturing date listed on the UL nameplate near the classification information.

Additionally, you should look at the gauge on the top of the extinguisher at least monthly. The needle should be in the green section. You’ll need to replace or recharge any extinguisher that’s been used or has damage to the hose or nozzle. 

Make checking your fire extinguisher a regular part of your home fire safety routine. When you check the batteries on your smoke alarm, check your extinguisher too.

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