Which fire hazard classifications require the use of dry chemical systems according to NFPA 17?

The correct answer identifies the fire hazard classifications that specifically require the use of dry chemical systems. According to NFPA 17, dry chemical extinguishing systems are particularly effective for Class B and Class C fire hazards.

Class B fires involve flammable liquids and gases, which can create explosive fire conditions. Dry chemical agents are highly effective at quickly suppressing these types of fires by disrupting the chemical reaction occurring in the fire and smothering the flames.

Class C fires involve energized electrical equipment. Since dry chemical agents can quickly extinguish these flames without conducting electricity, they are suitable for this classification as well. The rapid deployment of dry chemical agents can prevent further damage and ensure safety when working around live electrical systems.

Though Class A fires, which involve ordinary combustibles like wood, paper, and cloth, might also see the use of dry chemical systems, the primary focus of NFPA 17 is on Class B and Class C fires due to the unique properties and behaviors of the substances involved in these hazards. This makes them the appropriate classifications for the specific utilization of dry chemical extinguishing systems per the standard.