What is the primary extinguishing agent used in a Class D extinguisher?

The primary extinguishing agent used in a Class D extinguisher is specifically designed for dealing with fires that involve combustible metals, such as magnesium, titanium, and sodium. These types of fires cannot be effectively extinguished with water or standard chemical extinguishers because they can react violently with those agents.

A Class D extinguisher typically employs a dry powder, which serves as a non-reactive extinguishing medium. This dry powder works by smothering the fire and separating the fuel from oxygen, thereby disrupting the fire's chemical reaction. It is formulated to absorb heat and form a crust over the burning metal, effectively smothering the flames and preventing re-ignition.

Other options, such as water or carbon dioxide, are ineffective against Class D fires because they can exacerbate the reaction of the burning metal. Dry chemical extinguishers are suitable for other classes of fires but do not address the specific hazards associated with combustible metals. Thus, the information confirms that a non-reactive extinguishing medium is the correct choice for a Class D extinguisher.