Why should water not be used on class D fires?

Water should not be used on Class D fires because it may cause the fire to burn more violently and can lead to explosions. Class D fires involve combustible metals, such as magnesium or sodium, which react with water in a highly exothermic manner. When water comes into contact with these metals, it can produce flammable hydrogen gas, which ignites upon contact with the heat of the fire, potentially leading to an explosive reaction.

In the context of firefighting, the unique nature of these metals means that using water as an extinguishing agent is not only ineffective but can also make the situation significantly worse, as it exacerbates the fire rather than controlling it. Instead, specialized extinguishing agents, such as dry powder agents, are recommended for effectively smothering and isolating the burning metal without the risk of violent reactions. Understanding the chemical properties and behaviors involved in different classes of fires is crucial for safely and effectively managing fire emergencies.