If you look on your fire extinguisher and see what looks like an incredibly cryptic, unreadable code that looks something like 3A:21B:A, those numbers simply indicate the size rating of the agent inside the extinguisher itself. Also, the codes can tell you how effective the extinguisher is relative to other fire extinguishing apparatus.

Here’s the breakdown:

Class A size ratings discusses Water equivalency. So on the code the first number is 3A. Each number on that code represents 1 ¼ gallons of water. So above, our extinguisher is as good as 3 ¾ gallons of water. So 3A is the same as 3 ¾ gallons of water.

Class B Rating lets you know the range or square footage the agent can cover. On this code, it says 21B. The number is simply the range relative to feed. So if we took this extinguisher and sprayed it all over, we could cover about 21 square feet.

Class C rating is simply the class of fire extinguisher you’re using. In this case, it’s for ordinary fires.

Therefore, the full code: 3A:21B:A basically lets you know that this particular extinguisher shoots an agent the equivalent of about 3 ¾ gallons of water about 21 square feet – and is best used to put out ordinary fires.

So now you know! And if you need help trying to figure out what extinguishers are most relevant to your surroundings, please contact Protegis Fire & Safety.