Class D fires, also known as metal fires, involve combustible metals such as magnesium or lithium and are among the most dangerous types of fires. They require specific suppression methods and equipment—namely, Type D fire extinguishers—to ensure effective control and safety. In this guide, we explain what a Class D fire is, why it’s so hazardous, which extinguishers to use or avoid, and the best practices for prevention and preparedness.
What Are Class D Fires?
Class D fires involve highly reactive combustible metals such as sodium, magnesium, potassium, and lithium. These materials can ignite under heat, friction, or chemical reaction and burn at extreme temperatures. Unlike typical fires (Class A, B, or C), they require specialized extinguishing agents due to their unique behavior.
Why Class D Fires Are Especially Dangerous—and Easy to Get Wrong
Class D fires demand special attention because they burn at much higher temperatures than typical fires. Using water to extinguish them carries a high risk of explosion, making specialized prevention and response strategies essential.
Real Example: Pingtung Factory Explosion Caused by Combustible Chemicals and Metal Fire Hazards
A notable example is the fire at Mingyang International's Pingtung plant, a catastrophic event in September 2023. This explosion was triggered by a chemical reaction involving tert-butylcyclohexane at high temperatures. The Pingtung County government accused the company of illegally storing large quantities of hazardous materials, exacerbating the disaster’s severity (Source: Wikipedia).
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Which Fire Extinguishers Should Be Used—or Avoided—for Class D Metal Fires?
Type D fire extinguishers are specifically designed to suppress metal fires by smothering them with a dry powder that cuts off the oxygen supply without reacting with the metal.
⚠️ Use Specialized Metal Extinguishers
Fires involving metals like lithium, zirconium, and titanium are extremely dangerous and must be tackled using dedicated Class D extinguishers. Note that these extinguishers are exclusively for metal fires and should not be used on other fire types, which require dry powder, foam, or liquid-based solutions.
Further Reading: Different fires need different extinguishers—discover the 6 common types and their uses!
⚠️ Avoid Water-Based Extinguishing Agents
In a metal fire, panic or using the wrong extinguisher can lead to more dangerous situations. Applying water or water-based agents can cause intense oxidation reactions with the metal, rapidly intensifying the fire.
Preventing Metal Fires: Key Precautions
To prevent Class D fires, whether at home or in factories, follow these three key preventive measures:
Maintain Metalworking Equipment and Workspaces:
When performing high-temperature tasks or handling molten metals, wear protective gear such as heat-resistant clothing, gloves, and face shields to reduce the risk of burns or fires. Follow equipment manuals and safety protocols strictly.
Conduct Regular Inspections and Staff Training:
Extinguishers should carry a certified label and undergo inspection by qualified professionals every three years. Inspections check for deformation, corrosion, damage, and proper pressure gauge function. Train metalworking staff regularly to enhance risk awareness and emergency response skills.
Follow Protective Protocols During High-Heat Tasks:
Keep work areas clean and regularly inspect equipment, replacing worn or damaged parts promptly, especially those in contact with metals. Metal shavings and lubricants can pose fire hazards, so clean them frequently.
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How Does a Metal Fire Extinguisher Work?
Choosing certified fire extinguishers adds essential safety to homes and workplaces. For metal fires, a specialized dry powder extinguisher is indispensable.
Cheng Deh Fire Protection’s Type D fire extinguisher is engineered for maximum performance against Class D fires. Using MPA-certified Belgian dry powder agents, it effectively smothers reactive metal fires without causing explosive reactions. Housed in a 1.3mm steel cylinder and certified to EN 615:2009 and EN3 standards, this extinguisher is ideal for factories, metalworking plants, and laboratories.
Class D Fire / Type D Fire Extinguisher FAQ
What causes a Class D fire?
Class D fires are typically caused by heat, sparks, or friction igniting fine metal shavings or reactive metals like magnesium, titanium, or lithium.
Can I use a CO₂ or foam extinguisher on a metal fire?
No. Foam and CO₂ extinguishers are ineffective and potentially dangerous for metal fires. Only a certified Type D extinguisher should be used.
Where are Class D fire extinguishers commonly used?
They are essential in environments with combustible metals—such as automotive plants, laboratories, aerospace manufacturing, and battery production facilities.