Tennessee Wastewater Operator Practice Exam

Which class of fire extinguisher is safe for use on flammable liquids such as grease, gasoline, and oil?

1. Class A

2. Class B

3. Class C

4. Class D

The correct answer is: Class B

Class B fire extinguishers are specifically designed for combating fires that involve flammable liquids such as grease, gasoline, and oil. These extinguishers work by cooling the burning material and forming a barrier between the fuel and the oxygen, effectively suppressing the flames. Fires fueled by flammable liquids require agents that can extinguish flames without causing the liquid to spread or splatter, which is exactly what Class B extinguishers are equipped to do. Typically, these extinguishers contain either foam, dry chemical, or carbon dioxide as extinguishing agents. In contrast, Class A extinguishers are intended for ordinary combustibles like wood and paper; Class C extinguishers are suitable for electrical fires; and Class D extinguishers are used for combustible metals. Each class is tailored for different fire scenarios, making it essential to use the appropriate type in emergencies.