What Is a Class D Fire Extinguisher: Understanding In Detail

Have you ever wondered what it takes to tame a fire fueled by the most reactive and dangerous metals on the planet? For such events, you will need a class D fire extinguisher. What is a class D fire extinguisher?

A Class D fire extinguisher is specifically designed to combat fires involving combustible metals such as magnesium, sodium, titanium, and potassium. It contains a specialized extinguishing agent that can safely suppress and control fires fueled by these highly reactive metals.

Prepare to explore how this specialized extinguisher brings a new level of safety and control when facing the untamed power of metal fires. 

What Is a Class D Fire Extinguisher

Features of Class D Fire Extinguisher 

Here are some key features that make Class D fire extinguishers indispensable in combating fires involving combustible metals.

Specialized Extinguishing Agent: Class D fire extinguishers are equipped with a unique extinguishing agent specifically formulated to combat fires fueled by combustible metals. This agent is designed to smother and cool down the flames, effectively suppressing the fire.

Metal-Specific Applications: Class D extinguishers are tailored for fires involving specific combustible metals such as magnesium, sodium, titanium, potassium, and more. Each metal requires a specific extinguishing agent due to its varying combustion properties.

Non-Conductive Properties: They do not conduct electricity, minimizing the risk of electrical shock when combating metal fires involving live electrical equipment.

Powder Form: The extinguishing agent in Class D extinguishers is often in the form of a dry powder. This powder is highly effective in smothering the flames and preventing the fire from spreading further.

Heat Absorption: Class D extinguishers are designed to absorb and dissipate heat generated by metal fires. By reducing the temperature of the fire, they help prevent re-ignition and provide better control over the situation.

Unique Dispensing Mechanism: In order to effectively discharge the extinguishing solution, Class D fire extinguishers often use a specific dispensing mechanism. This system makes sure that the agent is applied to the fire in a controlled and targeted manner.

When to use a Class D Extinguisher?

A Class D extinguisher should be used when encountering fires fueled by combustible metals.  These extinguishers are specifically designed to address the unique challenges posed by Class D fires.

It is important to remember that traditional fire extinguishers, such as those used for Class A, B, or C fires, are not suitable for extinguishing Class D fires. You need class D for such a situation. 

When Not to Use a Class D Fire Extinguisher?

Class D extinguishers should not be used in the following situations:

Non-Combustible Materials

Class D extinguishers are specifically designed for fires fueled by combustible metals. They should not be used to extinguish fires involving non-combustible materials such as wood, paper, liquids, or non-metallic materials.

Unknown or Reactive Metals

If the type of metal involved in the fire is unknown or is a highly reactive metal, it is not recommended to use a Class D extinguisher. Different metals may require specific extinguishing agents, and using the wrong agent can be ineffective or potentially hazardous.

Lack of Training or Knowledge

Proper training and knowledge are essential when handling Class D extinguishers. If you are unfamiliar with their proper usage or have not received training on handling metal fires, it is best to leave the firefighting to trained professionals and evacuate the area safely.

Confined Spaces or Lack of Ventilation

Class D extinguishers should not be used in confined spaces or areas with limited ventilation. The use of certain extinguishing agents can release gases or deplete oxygen, creating potential health hazards in enclosed environments.

Different Types of Class D Fire Extinguishers

Here are some different types of Class D fire extinguishers used for combating fires involving combustible metals.

Type of Class D Fire ExtinguisherExtinguishing AgentTypical Applications
Sodium ChlorideSodium chloride-based extinguishing powderFires involving magnesium, sodium, potassium, and other alkali metals
Copper-basedCopper-based extinguishing powderFires involving lithium, titanium, and other reactive metals
Graphite-basedGraphite-based extinguishing powderFires involving magnesium, lithium, titanium, and other combustible metals
Sodium carbonateSodium carbonate-based extinguishing powderFires involving sodium, potassium, and other alkali metals
Potassium carbonatePotassium carbonate-based extinguishing powderFires involving potassium and other alkali meta

How to Refill Class D Fire Extinguishers?

Refilling Class D fire extinguishers should be done by certified professionals or authorized service centers to ensure safety and proper functionality. The process involves the following steps:

  • Discharge and Empty: Completely discharge the Class D extinguisher to ensure there is no remaining pressure or extinguishing agent.
  • Inspection and Testing: Thoroughly inspect the extinguisher for any damage or wear. Test the pressure gauge and other components to ensure they are in working condition.
  • Refill with Correct Agent: Refill the extinguisher with the appropriate Class D extinguishing agent specified by the manufacturer. This ensures compatibility and effectiveness.
  • Recharge and Reassemble: Recharge the extinguisher with the recommended pressure level as per manufacturer guidelines. Reassemble all parts, ensuring proper sealing and connections.
  • Certification and Documentation: Upon completion, certify the refill and update the service records with the date, agent used, and other relevant information.

What Are the Differences Between Class D and Class K Fire Extinguishers?

Class D and Class K fire extinguishers serve distinct purposes. While Class D extinguishers are designed to tackle combustible metal fires, Class K extinguishers are essential for suppressing fires caused by cooking oils and fats. Both extinguishers use different extinguishing agents, making crucial safety knowledge for class K fire extinguishers imperative in kitchens and restaurants. An understanding of the differences between these two types of extinguishers is crucial for effective fire management and prevention.

Precaution to Maintain for Class D Fire Extinguishers

Maintaining proper precautions for Class D fire extinguishers is crucial to ensure their reliability and effectiveness in combating fires fueled by combustible metals. Here are important precautions to keep in mind:

  • Storage and Inspection: Store Class D extinguishers in a designated area away from potential hazards and regularly inspect them for any signs of damage or deterioration.
  • Proper Handling: Follow the manufacturer’s guidelines for handling Class D extinguishers, including proper gripping and carrying techniques.
  • Training and Education: Provide proper training to individuals responsible for operating Class D extinguishers to ensure they understand their unique characteristics and limitations.
  • Compatibility: Use the appropriate Class D extinguisher specifically designed for the type of metal involved in a potential fire.
  • Regular Maintenance: Schedule regular maintenance and servicing by qualified professionals to check pressure levels, ensure the integrity of the extinguishing agent, and confirm overall functionality.


The Class D fire extinguisher stands as a remarkable tool crafted to combat the fierce and perilous fires fueled by combustible metals. With its specialized extinguishing agents and tailored techniques, it emerges as a vital lifeline in the face of metal fire challenges, ensuring efficient suppression and control. 

However, it is crucial to acknowledge that the successful utilization of Class D fire extinguishers demands a comprehensive understanding and appropriate training.