What type of extinguisher should not be used on combustible metals?

The correct choice is based on the specific properties and classifications of fire extinguishers. Class D extinguishers are designed exclusively for use on fires involving combustible metals, such as magnesium, titanium, and sodium. These materials require special extinguishing agents because traditional methods may exacerbate the fire.

When dealing with combustible metals, using the appropriate extinguisher is crucial. Class D extinguishing agents, often composed of dry powder, work by smothering the fire, preventing oxygen from reaching the burning material. Other types of extinguishers may introduce water or chemicals that can react violently with combustible metals, potentially making the situation worse rather than extinguishing the fire.

In contrast, Class A extinguishers are intended for ordinary combustibles like wood, paper, and cloth; Class B extinguishers are used for flammable liquids and gases; while Class C extinguishers are meant for electrical fires. None of these are suitable for combustible metals, which is why the use of a Class D extinguisher is essential for this type of fire.