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What’s the Significance of the Numbers on a Fire Extinguisher? January 16, 2018

Anchorage, Anchorage, AK
What’s the Significance of the Numbers on a Fire Extinguisher?, Anchorage, Alaska

Ever wonder what the string of numbers on your fire protection devices means? Understanding the significance of these different numbers and letters is an essential part of selecting the right fire extinguishers for your business needs. Read on to learn more about fire extinguisher size ratings and classes to ensure you’re up to the task.

What Are the Different Fire Extinguisher Classes?

The first letter you’ll notice on the side of your business’ fire extinguishers designates its classification. If it reads “Class A,” the fire protection device is designed to contain combustible flames ignited from plastic, paper, or wood. Class B extinguishers are meant to be used on fires started by flammable liquids, like gas, petroleum or oil. And, Class C devices are used for putting out electrical fires.

Since Class A, B, and C extinguishers are all meant for fires common in homes and workplaces, you’ve likely seen an ABC extinguisher. Class D devices are a little less common and designed for flames ignited by combustible metals, like titanium, sodium, or magnesium. Lastly, Class K extinguishers can be used to put out kitchen fires sparked by grease or flammable oil.

What Are the Different Size Ratings?

Ffire protectionire protection devices also come in different sizes based on each extinguishing class present. For example, say you have an extinguisher that reads 4A:20B:C. The Class A portion of the size rating (4A) notes that the contents are equivalent to 5 gallons of water, which can be used to extinguish the flames. Next, the Class B portion of the size rating (20B) explains that the device has enough power to cover 20 square feet of area when the nozzle is swept side to side.

And finally, the Class C rating is simply “C” because there is no relevant sizing necessary to put out an electrical fire. Containing this type of fire requires the same level of water and coverage distance to that of a non-conductive medium. It’s best to base your sizing decisions on the Class A and B portions to ensure you can successfully extinguish any Class C fires.


Need assistance selecting and purchasing fire extinguishers that are code-compliant for your business? Based in Anchorage, AK, North Star Fire Protection has been the area’s top choice in fire safety matters for more than 40 years. Put your business on the road toward safety today by calling them at (907) 677-1233. You can also learn more about the company’s fire sprinkler system installation and exit lighting services by visiting their website.

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