What is a Class D Fire Extinguisher?

what is a class d fire extinguisher

Fire safety is a paramount concern in any environment, from industrial settings to educational institutions. One of the specialized tools designed to combat specific types of fires is the Class D fire extinguisher. 

Understanding its purpose, usage, and the challenges it addresses is crucial for effective fire safety management. Keep reading below to learn more.

What is a Class D Fire Extinguisher?

A Class D fire extinguisher is specifically designed to combat fires involving combustible metals. These metals, which include magnesium, titanium, sodium, lithium, potassium, and zirconium, present unique challenges when they ignite. 

Combustible metal fires are classified under Class D due to the distinct nature of their chemical properties and the hazards they pose.

What is a Class D Fire Extinguisher Intended for Use On?

Class D fire extinguishers are intended for use on fires that involve combustible metals. These metals can ignite under specific conditions, such as high temperatures or chemical reactions, leading to intense and difficult-to-control fires. 

Traditional fire extinguishers, which are effective against common combustibles (Class A), flammable liquids (Class B), and electrical equipment (Class C), are typically ineffective and potentially hazardous when used on a combustible metal fire. This underscores the importance of using the correct type of extinguisher tailored for metal fires.

Extinguishing Agents for Class D

class d fire extinguisher

The extinguishing agents used in Class D fire extinguishers are designed to tackle the unique characteristics of metal fires. The primary agents include:

1. Dry Powder: The most common agent, dry powder extinguishers contain specific formulations that vary depending on the type of metal involved. For instance, sodium chloride (salt) is effective on magnesium, sodium, and potassium fires, while copper powder can be used on lithium fires.

2. Graphite-Based Compounds: These compounds form a crust over the burning metal, smothering the fire by cutting off the oxygen supply and dissipating heat.

3. Specialized Powders: Certain metals require unique agents. For example, a proprietary blend of chemicals may be necessary for titanium fires.

These agents work by creating a barrier between the metal and the oxygen in the air, thus interrupting the chemical reaction that sustains the fire.

Why Are Class D Fires Difficult to Extinguish?

Class D fires are notoriously difficult to extinguish for several reasons:

1. High Ignition Temperatures: Combustible metals often require extremely high temperatures to ignite. Once ignited, they burn at intensely high temperatures, complicating extinguishment efforts.

2. Reactivity: Metals like sodium and potassium react violently with water, releasing hydrogen gas, which can lead to explosions. This reactivity makes water-based extinguishing methods dangerous and ineffective.

3. Oxygen Dependency: Combustible metals burn by reacting with oxygen, and some metals can even draw oxygen from other compounds, making them self-sustaining in the absence of atmospheric oxygen.

4. Surface Area: When metals are in fine powder form, they have a large surface area that can ignite easily and spread rapidly, creating extensive fires that are hard to control.

benefits of class d fire extinguisher

How is a Class D Fire Extinguisher Used?

Using a Class D fire extinguisher involves specific steps to ensure safety and effectiveness:

  • Identify the Metal: Determine the type of metal involved in the fire. This identification is crucial because different metals require different extinguishing agents.
  • Apply the Agent: Using the extinguisher, apply the dry powder or granular compound directly onto the burning metal. It is important to apply the agent gently to avoid dispersing the burning material and causing the fire to spread.
  • Cover Completely: Ensure the entire fire is covered with the extinguishing agent. This coverage creates a barrier between the metal and the surrounding oxygen, helping to smother the flames.
  • Allow Cooling: After the flames are extinguished, allow the metal to cool completely. Premature disturbance can reignite the fire, posing further risks.

[Also Read: How to Use a Home Fire Extinguisher Safely]

Where is a Class D Fire Extinguisher Used?

Class D fire extinguishers are essential in environments where combustible metals are present. This includes:

  • Industrial Plants: Facilities involved in metal fabrication, casting, and processing.
  • Laboratories: Research and development settings where experiments with combustible metals take place.
  • Manufacturing: Industries producing metal components for various applications, such as automotive and aerospace sectors.
  • Storage Facilities: Warehouses storing significant quantities of combustible metals.

Need Help In Preventing Class D Fires?

Understanding the specific use and application of a Class D fire extinguisher is crucial for safety in environments where combustible metals are present. These extinguishers are specialized tools designed to combat the unique challenges posed by metal fires. 

By using the appropriate extinguishing agents and following the correct procedures, Class D fire extinguishers can effectively manage and extinguish these dangerous fires, ensuring a safer environment in industrial and laboratory settings.

To ensure your facility is fully equipped and your staff is trained to handle Class D fires, schedule a consultation with B&W Fire Security Systems in Prescott, AZ. Our experts can assess your specific needs, provide tailored fire safety solutions, and offer comprehensive training. Contact B&W Fire Security Systems today to enhance your fire safety preparedness and protect your valuable assets.



Need service – interested in a FREE quote? No problem! Just fill out the contact form and we’ll get back to you as soon as possible. You can also call us at 928-772-8008 or (800) 288-1005.