Associate Safety Professional Practice Exam

For which class of fire is foam considered an effective extinguishing agent?

1. Class A and B

2. Class B and C

3. Class C and D

4. Class A only

The correct answer is: Class A and B

Foam is considered an effective extinguishing agent primarily for Class A and Class B fires. Class A fires involve ordinary combustibles such as wood, paper, and textiles, while Class B fires pertain to flammable liquids like gasoline, oil, and grease. Foam works by creating a barrier between the fuel and the air, effectively extinguishing the fire by cutting off its oxygen supply and cooling the burning materials. For Class A fires, foam can help smother the flames while also cooling the hot surfaces to prevent re-ignition. For Class B fires, foam forms a blanket over the surface of the flammable liquid, preventing the vapors from igniting and suppressing the flames. Using foam on Class C fires, which involve energized electrical equipment, is not advisable, as foam can conduct electricity leading to further hazards. Similarly, Class D fires, which involve combustible metals, require specific extinguishing agents and methods that foam cannot provide. Therefore, foam is most effectively utilized for Class A and Class B fires, making this the correct answer.