What do the numbers and letters mean on a fire extinguisher?

Fire extinguishers use a classification system that uses letters and numbers. The letter represents the class of fire the extinguisher can be used on. The number represents the effectiveness. For instance, if a fire extinguisher has a 1-A rating, it can control class A fires and can dispense the equivalent of 1.25 gallons of water. A 2-A rated extinguisher controls class A fires and contains the equivalent of 2.50 gallons of water.
The effectiveness of class B extinguishers are measured a bit different. Class B extinguisher ratings are based on square footage. So a 10-B rating would allow the extinguisher to control a fire of 10 square feet.

Only class A & B extinguishers have a numerical rating that goes along with the letter. The other fire classes and their extinguisher equivalents will only display the letter.
So what do you think this code means on a fire extinguisher? 2-A:10-B:C

Answer: This extinguisher is approved for A,B, & C class fires. It has the equivalent of 2.50 gallons of water for class A fires, and has a 10 square foot covering distance for class B fires. It also uses a non-conductive agent that is good for class C fires.

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