Which classes of fire extinguishers have numerical ratings?

The classes of fire extinguishers that have numerical ratings are Class A and Class B extinguishers. Class A extinguishers are rated based on their ability to extinguish ordinary combustibles, such as wood, paper, and cloth, with the numerical rating indicating the size of the fire they can handle. For example, a Class A extinguisher with a rating of 2-A can extinguish a fire that is equivalent to 2.5 gallons of water.

Class B extinguishers are rated for flammable liquids and gases, such as gasoline or oil. The numerical rating for Class B extinguishers usually corresponds to their effectiveness against given sizes of flammable liquid fires. For instance, an extinguisher rated 5-B would indicate its capability to extinguish a fire involving a certain volume of flammable liquid.

Classes C (electrical), D (metal), and K (cooking oils and fats) do not have numerical ratings assigned to them in the same way that Class A and Class B extinguishers do. Class C extinguishers are more about the type of fire they are intended for rather than a measure of effectiveness, while Class D and K extinguishers are generally used for specific applications or materials without a