Fire Extinguisher Series – Class D Extinguishers & How to Clean Up After Them

All metals under the right conditions can combust—for example, iron in the form of steel or aluminum. They are used in the manufacture of structures. In principle, they are considered non-combustible materials but these same materials in the form of aluminum powder or chips or fine fibers in the case of iron can easily ignite and that very intensely.

Here we are talking about the Class D fires caused by metals, such as magnesium, titanium, potassium and sodium, etc., that can be extinguished only by Special powders extinguishers.

Let’s discuss the type of fire extinguisher suitable for Class D fires and some tips on how to clean up after Class D Extinguishers!

Class D Fires

Class D fires are the ones that have some type of metal as fuel (such as magnesium, potassium, sodium, aluminum, etc.).

All combustible metals and those that also easily ignite usually produce very violent combustion reactions, with high-speed and strongly exothermic oxidation processes, with a release of heat per unit of measure, much greater than, for example, the most combustible liquids. This occurs in the event that they are in the form of settled dust because if the dust is in suspension, the combustion is so violent that it may result in an explosion.

Class D Fire Extinguishers

It is not possible to use water to extinguish class D fires. We must also remember that the combustion of these metals, such as magnesium or sodium, is due to an oxy-reduction process rather than oxidation, which means that it can occur without oxygen. They have such a burning capacity and a high affinity for oxygen that they can continue to burn on fire extinguishers commonly used to extinguish type A, B and C fires (such as carbon dioxide or nitrogen).

In addition, the use of water in any of its forms is totally ruled out for the extinction of class D fires. Some metals such as potassium or sodium spontaneously combust on contact with it in a rapid and strongly exothermic reaction that usually ends in an explosion.

For these reasons, the extinction of this type of fire is so delicate, and the means of fighting them must be chosen specifically. For now, it is not advisable to approach this type of fire without the adequate provision of autonomous breathing equipment and protective clothing.

It is also advisable to install automatic or remote control systems to minimize the presence of people in the vicinity. Early detection and rapid intervention away from the fire area of ​​other metals or combustible materials to reduce the amount is another good measure in this regard.

The fire extinguishers used in Type D fires are grouped under the name of Special Powders, which are a set of mixtures of varied composition and dosage and that each manufacturer patents.

Special Powder Extinguishers

Special Powder fire extinguishers can notably extinguish class D fires. They are similar to dry chemicals, but they separate oxygen from the fuel or remove heat. The powder comes out through a hose with an expanding end. They are only effective on Class D combustible metal fires. These extinguishers are reserved for use by fire-fighting professionals or in high-risk premises where metals are stored (industrial environment).

Sodium Chloride in Dry Powder

Some may contain as an extinguishing agent a mixture of sodium chloride in dry powder, very effective with fires with magnesium, sodium, potassium or aluminum powder.

With this one, the size of the particles is controlled to obtain optimum extinguishing efficiency based on sodium chloride with additives. The additives are tricalcium phosphate to improve its flow characteristics and metal stearates for hydrophobization.

Thermoplastic material is added to bind the sodium chloride particles into a solid mass under fire conditions. It is non-combustible, and its application against burning metals does not produce secondary fires. There is no known health hazard from the use of this agent. It is non-abrasive and non-conductive.

Copper Powder Fire Extinguisher

Others are based on copper powder (a large-capacity extinguishing agent). It is used for fires related to materials such as lithium.

The copper powder has been found to out-extinguish many agents. With dry powder whose particles are of uniform size, it is possible to put out lithium fires more quickly and effectively than existing agents.

In the quenching process, a non-reactive copper-lithium alloy is created, which preferentially forms on the surface of the molten lithium. The alloy becomes an exclusion barrier between the air and the molten metal, preventing reignition and favoring unreacted lithium cooling.

How to Clean Up After Class D Extinguishers

Since Class D fire extinguishers are reserved for professional use only, their residue should also be cleaned up by fire damage restoration professionals. However, below are some tips to follow in case you need to carry out immediate cleaning:

• Special Powder Dry powder agents are generally safe but may cause respiratory problems, eye damage, or skin irritation. Therefore, you must take the necessary precautions, such as masks, glasses and gloves, if the cleaning causes dry dust to be raised.
• Mono ammonium phosphate is a corrosive chemical and must be handled with care. Since some extinguishing agents need to be cleaned as soon as possible to prevent corrosive properties from causing damage, make sure the area you’re cleaning is completely cool to work on.
• As in any deep cleaning, you will remove furniture, objects and larger debris. Keep in mind that metal surfaces are the first to be damaged by these products; you should clean them first.
• To start cutting down on all the debris left behind by a fire extinguisher, most people recommend using a powerful enough vacuum.
• With a clean and slightly moistened cloth, you can collect the remains that still remain.
• A mixture based on plenty of water and vinegar will help to finish cleaning the areas where the product has managed to cling more intensely. Some people prefer to scrub only with soap and water, but if the extinguishing agent is more powerful, the water + vinegar solution may be better
• Once the cleaning is finished, it is highly recommended to ventilate well.

Now you know how to clean up after class D extinguishers, but it is still recommended to seek professional help. Sensitive and delicate items such as artwork, electronic equipment, and kitchen equipment will require professional cleaning if exposed to class D fire extinguishers.

If you live in Ventura County or its surrounding area and looking for a fire damage restoration service near you, contact 911 Restoration of Ventura County. The 911 Restoration of Ventura County team has certified and trained professionals who can clean all types of residues and remove soot, smoke, and water from the property after a fire. Call (805) 212-1154 or visit their website for more information.