Answer :
Final answer:
The statement is A) true; multipurpose dry chemical extinguishers are not effective on Class D (combustible metals) and Class K (commercial kitchen fires) fires. Class D requires special extinguishing agents, and Class K requires a fluorinated solution or other wet chemical agents.
Explanation:
The statement that multipurpose dry chemical extinguishers are effective on all classes except D and K fires is A) True. These extinguishers are generally suitable for Class A (ordinary combustibles), Class B (flammable liquids and gases), and Class C (energized electrical equipment) fires. However, they are not recommended for Class D fires, which involve combustible metals like magnesium, and Class K fires, which involve cooking oils and fats found in commercial kitchens. For Class D fires, specialized extinguishing agents such as sand or specific Class D dry chemical extinguishers are required because magnesium, for example, can react with water or carbon dioxide, exacerbating the fire. For Class K fires, a fluorinated solution or other wet chemical extinguishing agents that can form a barrier between the fuel and the oxygen are used since they are able to spread across the burning surface and extinguish the fire effectively.
