Fire Extinguisher Numbers Explained

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Understanding fire extinguisher numbers helps you choose the right type of equipment for your situation.
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Fire safety shouldn't be an afterthought. Both smoke alarms and fire extinguishers are essential pieces of fire safety equipment every home should have. Fire extinguishers in your house, garage, car and camper help you put out small fires quickly before they spread, but deciding on the right fire extinguisher can be confusing. The numbers and letters printed on fire extinguishers provide information about the tool. Understanding those ratings helps you pick the best extinguisher for different areas of your home.


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Fire Extinguisher Letter Ratings

Letter ratings on fire extinguishers describe what type of fire they can extinguish. Type A extinguishers put out ordinary fires of combustible material such as cloth or wood. A pictogram of a campfire next to the letter A is often printed on the units. Think A for ashes, since these types of material leave ashes when they burn.

Type B extinguishers put out fires caused by flammable liquids such as gasoline, solvents and grease. These are items that can be sold in barrels, so think B for barrel. C extinguishers put out electrical fires. Think C for current.


Most home fire extinguishers are labeled for A, B, C or all three. You'll sometimes see fire extinguishers labeled D. These can extinguish fires caused by burning metals such as magnesium. These are very dangerous fires you shouldn't try to put out yourself. Think D for don't touch.

Fire Extinguisher Numbers

Type A and B fire extinguishers have numbers next to them to show how much capacity they have to put out fires. A number next to an A on a fire extinguisher relates the contents of the extinguisher to an equivalent amount of water. Each number equals 1.25 gallons of water. So a "1" next to the A means the extinguisher has the equivalent of 1.25 gallons of water, a "2" equals 2.5 gallons and so on.


Numbers with the letter B refer to how many square feet of fire the extinguisher can put out. So 4B means the fire extinguisher can douse a 4-square-foot fire caused by flammable liquids. Class C extinguishers don't have any numbers associated with them.

Many home fire extinguishers are rated to put out more than one kind of fire. You might find a fire extinguisher labeled 2A10BC. This extinguisher contains the equivalent of 2.5 gallons of water, can put out about 10 square feet of flammable liquid fire, and can extinguish electrical fires.

Considerations for Fire Extinguishers

The larger the number of the fire extinguisher, the larger the area of fire you could put out. But bigger fire extinguishers are often heavy and take up a lot of space, making them inconvenient for most homes. Plus, it's dangerous to try to put out a large fire yourself. Instead of one very large fire extinguisher, consider keeping several smaller fire extinguishers in your home.


Fire Extinguisher Safety

Mount fire extinguishers within easy reach of areas where you're most likely to experience a fire, such as the kitchen and garage. You can buy fire extinguisher mounts if yours doesn't come with one. Familiarize yourself with the extinguisher's operation. Most extinguishers require you to pull a pin or move a switch, aim at the fire and press a trigger.

Fire extinguishers work best on small fires, such as a burning wastebasket or a small grease fire confined to a pan. Don't try to fight a large fire on your own. Leave the house and call emergency services.



Cynthia Myers

Cynthia Myers is the author of numerous novels and her nonfiction work has appeared in publications ranging from "Historic Traveler" to "Texas Highways" to "Medical Practice Management." She has a degree in economics from Sam Houston State University.