What is a Class D Fire Extinguisher Used For?

Posted August 06, 2019 by Koorsen Fire & Security

Not all fires are created equal, which is why a classification system has been developed to help identify different types of fires. These classes are determined by the fuel source of the fire. Furthermore, the class of fire also determines what type of extinguishing agent, or class of extinguisher, will be effective in putting that fire out. 

One class of fire that is lesser-known and not as common is the Class D fire. Class D fires can be extremely hazardous and require very special types of extinguishers to put them out. 

Read on to learn more about what a Class D fire is and what types of extinguishers qualify as Class D fire extinguishers. 

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Class D fires are those that occur from combustible metals, such as aluminum, titanium, magnesium, lithium, zirconium, sodium, and potassium. 

These types of fires usually occur in industrial, manufacturing, or laboratory settings when the metal fines - tiny, thin pieces of metal, often shavings or dust generated during the machining process ignite, becoming the fuel element in the fire triangle (fuel, oxygen, heat plus a chemical reaction). 

Class D fires can cause significant damage and are not simple to put out. 


Unfortunately, Class D fires cannot simply be extinguished with water or just any extinguishing agent. Water interacts with the combustible metal intensifying the fire, increasing the heat and spreading molten metal. 

Thus, it is imperative that only a Class D fire extinguisher is used to extinguisher a combustible metal fire. The best way to extinguish these fires is by smothering them & eliminating the oxygen element. The agent also helps to absorb the heat from the fuel.

To date, the only type of Class D fire extinguisher is the Dry Powder extinguisher. The powder agent used may be either powdered graphite, granular sodium chloride or copper based, all of which are effective at separating the fuel (the ignited combustible metal) from the oxygen. 

While dry powder extinguishers are effective for Class D fires, they are not effective for any other class of fire. 

It is important that those working around combustible metals understand the unique properties of Class D fires as well as how (and when) to properly and safely operate a Class D fire extinguisher.


Do you own, manage, or work in a setting that handles combustible metals? If so, it is vital that you and your employees are protected by a Class D fire extinguisher. 

If you are unsure whether or not you have the best fire extinguisher for your 

hazards, call the experts at Koorsen. They can help make sure that you and your property are protected by the most effective extinguishers for your setting. Koorsen can also provide you and your employees with fire extinguisher training to increase everyone’s safety. Contact them today.

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Topics: Fire Extinguisher

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Disclaimer: The information in this article is for informational purposes only. It is believed to be reliable, but Koorsen Fire & Security assumes no responsibility or liability for any errors or omissions in the content of this article. It does not constitute professional advice. The user of this article or the product(s) is responsible for verifying the information's accuracy from all available sources, including the product manufacturer. The authority having jurisdiction should be contacted for code interpretations.