What is a common chemical used in combating Class D fires?

Dry powder agents are specifically designed to extinguish Class D fires, which involve combustible metals such as magnesium, titanium, and sodium. Unlike other classes of fires, Class D fires require agents that can effectively smother the burning metal and prevent it from reacting with water or other standard extinguishing agents that could potentially worsen the fire.

Dry powder agents work by creating a barrier between the metal and the oxygen in the environment, thereby interrupting the combustion process. These agents are typically made from materials like sodium chloride or other metal powders that can absorb heat and create a cooling effect, which is essential for efficiently extinguishing these types of fires. This specialized approach ensures the safety of both the firefighters and the environment when dealing with highly reactive materials.

In contrast, using water or foam suppressants on Class D fires can lead to violent reactions, as these materials can exacerbate fires involving combustible metals. Carbon dioxide extinguishers are also not effective in this context, as they rely on displacing oxygen, which is not sufficient for extinguishing metal fires. Therefore, dry powder agents are the most appropriate choice for combating Class D fires.