Class D fire extinguisher

A Class D fire extinguisher is used to extinguish metal fires. The fire extinguisher contains either sodium chloride or copper powder and pressurized with nitrogen.

Sodium chloride
A special blended sodium chloride based dry powder extinguishing agent. Heat from the fire causes it to cake and form a crust excluding air and dissipating heat from burning metal. Metal fires involving magnesium, sodium, potassium and sodium-potassium alloys can be successfully extinguished with this extinguisher. There is data showing that zirconium, uranium, titanium, and powdered aluminium fires can be controlled and extinguished with this agent.

Copper
Developed by the U.S. Navy for fighting lithium and lithium alloy fires. The copper compound smothers the fire and provides an excellent heat sink for dissipating heat. Copper powder has been found to be superior to all other known fire extinguishing agents for lithium.