Tennessee Wastewater Operator Practice Exam

Which class of fire extinguisher is safe for use on ordinary combustible fires, such as those fueled by paper or wood?

1. Class A

2. Class B

3. Class C

4. Class D

The correct answer is: Class A

The Class A fire extinguisher is specifically designed for ordinary combustible materials, which include common items such as paper, wood, cloth, and some types of rubber. These materials are prevalent in everyday settings and are categorized as Class A fires due to their ability to burn in a way that creates embers and ash during combustion. Class A extinguishers typically utilize water, foam, or certain dry chemical agents to combat fires effectively by cooling the burning material and removing heat from the combustion process. They can reduce the fire temperature to below the ignition point of the combustible material, thus extinguishing it. This makes them the appropriate choice for addressing fires that start from everyday materials found in homes and offices. In contrast, other classes of fire extinguishers are used for different types of fires. Class B extinguishers are suited for flammable liquids and gases, Class C extinguishers are intended for electrical fires, and Class D extinguishers are designed for combustible metals. Each class has specific characteristics that determine their effectiveness and safe application, making it crucial to match the right extinguisher to the type of fire.