Which type of hazard requires a dry chemical system according to NFPA 17?

The selection of a dry chemical extinguishing system is aligned with its effectiveness in combating specific types of hazards. According to NFPA 17, dry chemical agents are particularly suited for Class B and Class C hazards.

Class B hazards encompass flammable liquids and gases, which can ignite readily and spread fire rapidly. Dry chemicals, such as sodium bicarbonate or monoammonium phosphate, are effective in smothering these types of fires by interrupting the combustion process and preventing the release of flammable vapors.

Class C hazards involve energized electrical equipment. Dry chemical extinguishers are non-conductive, making them safe to use on electrical fires without posing a risk of electrical shock to the user.

While Class A hazards involve ordinary combustibles like wood, paper, and cloth, they are usually addressed with water-based extinguishers or foam systems that better suit those materials. Class D hazards, which involve combustible metals, and Class K hazards, related to kitchen fires involving cooking oils and fats, necessitate specific extinguishing agents that are distinct from dry chemical systems.

Thus, the applicability of dry chemical systems according to NFPA 17 makes them ideal for effectively managing Class B and Class C fire hazards.