Firefighter Practice Exam

A 2 ½-gallon fire extinguisher that contains water under pressure is found without a classification label. Which class of fires does it effectively suppress?

1. Class A

2. Class B

3. Class D

4. Class C

The correct answer is: Class A

A 2 ½-gallon fire extinguisher filled with water under pressure is specifically designed to combat Class A fires. Class A fires involve ordinary combustible materials such as wood, paper, cloth, and some plastics. Water is effective in extinguishing these types of fires as it cools the burning materials and reduces the ambient temperature below the ignition point. Fire extinguishers designed for other classes of fires, like B, C, or D, use different agents that are more suitable for flammable liquids, electrical fires, or combustible metals. For example, Class B fires typically require foam or dry chemical agents, Class C involves non-conductive agents to prevent electrical hazards, and Class D necessitates specialized extinguishing materials that can handle combustion of metals. Since water can conduct electricity and is ineffective for flammable liquids, it is critical to use the right extinguisher for varying fire types. Therefore, the water-filled extinguisher is relevant and effective only for Class A fires.