Class D fires are those involving burning metals. This type of fire can be found anywhere there are metal “fines,” filings or particles including metal fabrication facilities, warehouses, labs, and factories. Not all metals are flammable, but those that are can be very difficult to extinguish once they start to burn.

Most often, these fires involve magnesium and titanium, but they can also involve:

• Sodium
• Potassium
• Sodium-potassium alloys
• Plastics
• Zirconium
• Lithium

To put out combustible metal fires, a Class D extinguisher is the only recommended option. When used properly to extinguish a metal fire, the agent in a D-rated fire extinguisher will form a crust over top of the fire to absorb the heat and smother the fire robbing it of oxygen and preventing it from spreading.