Dry powder as a fire extinguisher is used on:

Dry powder fire extinguishers are particularly effective for Class D fires, which involve combustible metals such as magnesium, titanium, and sodium. These materials ignite and burn at extremely high temperatures, and traditional extinguishing agents like water can exacerbate the fire or create hazardous reactions.

Dry powder extinguishers contain specific agents designed to smother these types of fires and prevent oxygen from fueling the combustion process. Additionally, they effectively absorb heat and control the reaction of the burning metal with oxygen, making them suitable for situations that involve flaming metal.

In contrast, Class A fires involve ordinary combustible materials like wood and paper, Class B fires pertain to flammable liquids, and Class C fires involve electrical equipment. Using dry powder extinguishers in these contexts may not be appropriate or effective, highlighting why they are specialized for Class D fires.