What does the number on a fire extinguisher signify?

The number on a fire extinguisher indicates the relative size of the extinguisher. Fire extinguishers are classified with numbers that usually refer to the weight of the contents in pounds. For example, a 2-A rating would suggest that the extinguisher is able to handle class A fires that require a certain amount of water equivalent to that of 2.5 gallons. Hence, the numbers help users to choose the appropriate size for different fire risks based on the area or situation they may be dealing with.

In contrast, while the fire extinguisher does indicate the type of fire it can extinguish through letters or symbols, the specific number itself focuses solely on the size aspect. The brand is not represented by the number, and the expiration date is typically indicated elsewhere on the label, not as part of the numerical information. Therefore, understanding the significance of the number helps users to determine which extinguisher is suitable for their needs in terms of capability and capacity.