Which class of fire extinguisher includes a number in its classification?

The class of fire extinguisher that includes a number in its classification is Class A. This classification system indicates the type of materials that the extinguishing agent is effective against. Class A fire extinguishers are designed to combat fires involving ordinary combustibles such as wood, paper, textiles, and some plastics. The "A" classification is also accompanied by a number that designates the relative effectiveness of the extinguisher for extinguishing these types of fires. The higher the number, the more effective the extinguisher is against Class A fires.

For example, a Class A extinguisher rated 2A is more effective than one rated 1A, with the number indicating the extinguisher’s capability in terms of fire fighting efficacy. In contrast, Classes B, C, D, and K have distinct classifications but do not use a numerical rating in the same way, often referencing the type of flammable substances they are designed to extinguish instead. Class K specifically addresses kitchen fires involving cooking oils and fats, while Class D is tailored for combustible metals.