What is the definition of dry powder in the context of fire extinguishers?

In the context of fire extinguishers, dry powder refers to a solid material in powdered form that is specifically designed for extinguishing class D fires, which involve combustible metals such as magnesium, sodium, and potassium. Dry powder fire extinguishers work by smothering the fire and forming a barrier between the combustible metal and the surrounding air, effectively preventing re-ignition.

This type of extinguishing agent is critical for class D fires because traditional extinguishing agents like water can react violently with combustible metals, potentially causing explosions or spreading the fire further. Therefore, using a dry powder extinguishing agent is essential for safely managing these specific types of fires.