Commercial Driver License (CDL) Class B Practice Test

In which scenarios is a B:C fire extinguisher not effective?

1. Combustible metals, wood, and paper

2. Electrical fires and vehicle fires

3. Gasoline and oil fires

4. Cooking fires and liqueurs

The correct answer is: Combustible metals, wood, and paper

The effectiveness of a B:C fire extinguisher is related to the types of fires it is designed to combat. A B:C extinguisher is specifically made for use on flammable liquids (like gasoline and oil) and electrical fires, making it effective in scenarios where these materials are involved. In the scenario involving combustible metals, wood, and paper, a B:C fire extinguisher would not be effective. The reason is that such fires require different types of extinguishers for efficient suppression. Fires involving wood and paper are classified as A-type fires, which are best extinguished with water or other agents specifically designed for solid combustibles. Similarly, combustible metals require extinguishing agents that do not react with the metals, which B:C extinguishers cannot provide. Thus, areas where wood, paper, and combustible metals are present would render a B:C extinguisher ineffective.