Class 5 Boiler Practice Exam

Which chemical agent is used to extinguish class C fires?

1. Water

2. CO2

3. Foam

4. DCP

The correct answer is: CO2

Class C fires involve energized electrical equipment, which introduces the risk of electrocution if traditional extinguishing agents such as water are used. The correct answer, carbon dioxide (CO2), is effective for extinguishing these types of fires because it displaces oxygen, thereby suffocating the fire while being non-conductive. This prevents any risk of electric shock that could occur if water were used. Carbon dioxide is also beneficial because it leaves no residue, making it suitable for use on sensitive electronic equipment found in environments where Class C fires may occur. This property is particularly important for maintaining the integrity of equipment after a fire has been extinguished. In contrast, other agents like foam and dry chemical powder (DCP) are less appropriate for use on Class C fires; foam can conduct electricity, and while dry chemical agents can be effective, they may leave a residue that can be harmful to electrical components. Therefore, CO2 stands out as the safest and most effective option for extinguishing Class C fires.