Which class of fire extinguisher has a rating of up to 640B?

Class B fire extinguishers are specifically designed to combat flammable liquids and gases, such as gasoline, grease, and oil. The rating of up to 640B indicates the effectiveness of the extinguisher in terms of the volume of flammable liquid it can extinguish; the higher the number, the more challenging the fire it can handle and the larger the area it can cover.

This rating is significant because it provides critical information for individuals responding to a fire involving flammable liquids. Professionals and responders can quickly assess the capability of a Class B extinguisher and its suitability for a particular situation, ensuring they can take appropriate action to mitigate the fire hazard safely.

In contrast, Class A extinguishers are meant for ordinary combustibles like wood and paper, Class C extinguishers are used for electrical fires, and Class D extinguishers are designated for combustible metals. Each class has distinct purposes and does not cater to the specific challenges posed by flammable liquids, making Class B the correct choice for this rating.