Which method is essential for extinguishing Class D fires?

Class D fires involve combustible metals such as magnesium, titanium, and sodium. The primary method for extinguishing these types of fires is to smother the fire with a material that can absorb the heat and remove oxygen from the environment, preventing the metal from igniting further oxygen.

Sand is particularly effective because it does not react with these metals, creating a barrier and cooling the flames without causing an explosion or a hazardous reaction, which could occur with water, steam, or foam. Water and steam can react violently with burning metals by causing them to ignite or explode, while foam isn't appropriate due to its water content, which may lead to similar dangerous reactions. Thus, using sand is the safest and most efficient approach to extinguishing Class D fires.