G2 Gas Fitter Practice Exam

What class of fire would be fought using a water filled extinguisher?

1. A

2. B

3. C

4. D

The correct answer is: A

A water-filled extinguisher is designed specifically for class A fires, which involve ordinary combustible materials such as wood, paper, cloth, and some plastics. These materials combust and produce ash, making water an effective extinguishing agent since it cools the burning material and removes the heat necessary for the fire to continue. Using water on class A fires works by soaking the materials and diminishing their temperature below the ignition point, thus suppressing the fire. Water does not chemically react with the burning substances but rather serves to absorb heat. In contrast, highlighting other classes helps clarify why water is not suitable for them. Class B fires involve flammable liquids and gases, where using water can spread the fire further rather than extinguish it. Class C fires involve electrical equipment, and employing a water extinguisher could create a risk of electric shock. Class D fires consist of combustible metals, which can react violently with water, making it an inappropriate choice. Therefore, knowing that class A fires are the only category where water-filled extinguishers can be effectively used helps solidify the understanding of fire classes and response.