How to Clean Up Fire Extinguisher Residue

Posted January 21, 2020 by Koorsen Fire & Security

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No one today would argue the benefits of portable fire extinguishers. According to the latest data, portable fire extinguishers are extremely effective in controlling small fires. But some of them do leave a mess to clean up, which in some cases can cause additional damage if not done quickly. This post will provide some guidelines for cleaning up fire extinguisher residue and address some of the common safety concerns associated with the task.

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While fire extinguishers may look a lot alike, they can, in fact, be very different. Fire extinguishers contain different chemicals based on the type of fires they are designed to extinguish. Different extinguishing agents can require different cleanup methods and unique safety precautions. So, you need to know what type of residue you’re working with.

Common extinguishing agents include dry chemicals, wet chemicals, and clean agents. All fire extinguishers are required to be labeled with either a sticker and/or a tag that identifies the type of fire extinguisher it is and the type of extinguishing agent it contains.


Fire extinguishing residues are generally non-toxic, particularly in the amounts you might expect when cleaning up after the use of a portable fire extinguisher. There are a few general precautions you should take regardless of the type of fire extinguisher used, as some can irritate the skin. Always avoid direct contact with any residue by wearing latex or rubber gloves to protect the hands and clothing that covers the arms and legs.

Cleaning up fire extinguisher residue typically does not require expensive personal protective equipment (PPE). However, the chemicals in some fire extinguishers can also cause significant irritation to mucous membranes in the nose and mouth if inhaled and can irritate the eyes. For these types of clean-ups, it is important to wear a dust mask and safety goggles. Dust masks with a NIOSH rating of N95 or N100 will filter out 95-100 percent of the tiny particles found in fire extinguishers.

Before cleaning begins, you should always consult the material data safety sheets (MSDS), now called safety data sheets (SDS). Both provide extensive and detailed information regarding the chemicals in the residue you will be cleaning up, including any safety risks and appropriate types of first aid.

For most fire extinguisher residues, basic first aid includes:

  • For skin exposure, wash with soap and water.
  • For eye exposure, flush the eyes with water until the pain or irritation goes away.
  • If residue is inhaled, get to an area with fresh air.
  • If skin and/or eye irritation persists, or if a person is experiencing a shortness of breath, seek medical attention.

First aid information is provided here to simply to underscore the fact that fire extinguisher chemicals are generally quite safe. Nonetheless, it is still important to always take the time to consult the MSDS/SDS before clean-up begins to ensure that you know all the risks involved as well as the proper way to dispose of the chemical residue collected.

Ideally, there will be a hard copy of the applicable MSDS/SDS onsite. However, if not, you can find MSDS/SDS for the substances contained in a fire extinguisher online by searching the manufacturer’s website using the model number on the fire extinguisher’s label. You can also use this searchable database.


Dry chemical fire extinguishers work with a pressurized spray of a dry chemical that will blanket a fire and extinguish it. The most common agents used in dry chemical fire extinguishers are monoammonium phosphate and sodium or potassium bicarbonate. Time is of the essence when this type of extinguisher is used because these powders can be corrosive to metals and can lead to further damage if not cleaned up quickly.

Any electrical contacts with residue on them should be cleaned with an electrical contact cleaner, which is typically a compressed air canister containing a cleaning agent that evaporates quickly, such as isopropyl alcohol.

It is always a good idea, if possible to first shut down the ventilation system in the area to be cleaned to avoid resuspending the powdery residue. It may be tempting to vacuum it up. But before you do, you need to know specifically what type of dry chemical agent was used.

Monoammonium Phosphate Residue

Monoammonium phosphate fire extinguishers are used to put out Class ABC fires. This type of residue must be cleaned by hand because it can irritate the skin and eyes if resuspended in the air with a vacuum cleaner. If this type of extinguisher was used, you can remove residue from the floor by wet-sweeping or sweeping with a dust suppressant.

Monoammonium phosphate residue on surfaces should be wiped away with a clean, dry cloth or brush. According to a 2013 study, soot erasers were also found to be effective for cleaning dry chemical residue on some types of materials. Soot erasers are sponges made of natural rubber that can be used to lift away dust, dirt, and soot from dry surfaces without getting it wet.

For surfaces that can be safely wet-washed, a cleaning paste made with equal parts baking soda and hot water can be used. Once applied, the paste should be allowed to sit on the surface for a few minutes before wiping it away with a damp cloth. Residue that has hardened or adhered to surfaces can be cleaned with a 1:1 solution of isopropyl alcohol and warm water, which will help to break down the silicone used in this type of extinguishing agent.

Sodium and Potassium Bicarbonate Residues

Sodium bicarbonate (baking soda) fire extinguishers and potassium bicarbonate extinguishers (also known as PKP or “Purple-K” based on its violet color) are used to put out Class B and some Class C fires.

Sodium and potassium bicarbonate residues are not as caustic as monoammonium phosphate residue. Given this, they can be safely removed with a vacuum equipped with the high-efficiency particulate air (HEPA) filter.

Bicarbonate-based residues on surfaces can be cleaned in the same manner as monoammonium phosphate with a clean, dry cloth or brush. For surfaces that can be safely wet-washed, an effective cleaning solution for these types of residue can be made by adding approximately three ounces (six tablespoons) of vinegar to a gallon of hot water.[2]

Class D Dry Powder Fire Extinguisher Residue

Another type of dry chemical fire extinguisher is the Class D dry powder extinguisher, which is used specifically for combustible metal fires that can occur in industrial, manufacturing, or laboratory settings where there may be concentrations of metal shavings and/or dust that could ignite. The extinguishing agent used in Class D dry powder fire extinguishers will vary based on the specific types of metals found in the setting they are used to protect but will usually contain one of the following:

● Sodium chloride

● Sodium carbonate

● Copper

● Graphite

Some of these residues will clean easily, while others may require the assistance of professionals who are equipped to address the specific requirements of each. Graphite-based powders, for example, are sensitive to static charge and can become combustible if airborne making it dangerous to clean with a vacuum. Given the different types of agents used in Class D fire extinguishers, it is important to first consult the MSDS/SDS before attempting a clean-up.


Class K wet chemical fire extinguishers are used in commercial kitchens to fight cooking fires. These extinguishers use a wet mixture of alkaline chemicals such as potassium carbonate, potassium acetate, or potassium citrate that turns into a foam, which blankets the fire depriving it of oxygen.

Because this type of extinguisher is used primarily in commercial kitchens and around cooking appliances, one of the most important steps is to turn off all power to any equipment prior to cleaning it. Make sure everything is completely dry before turning any power back on for any appliance.

Residue from Class K extinguishers usually clean up well with hot water and soap. Do not spray the foam with water as that will only create more foam, making a bigger mess. The best approach here is to vacuum, pump, or use absorbent materials to collect the foam. Any residue vacuumed with a wet vac should be bagged for proper disposal. If absorbent materials are used, they should be bagged for disposal as well. Once the bulk of the foam is removed, you can use soap and water to clean up any remaining residue.

It is essential to sanitize the entire area after removing fire extinguisher residue. All dishes, cookware, and utensils exposed should be washed, and any food that has come in contact with fire extinguisher residue should be discarded. Any cloth with residue on it can be washed in a clothes washer with regular laundry detergent.

As with all fire extinguishing agents, it is very important to consult the MSDS or SDS to determine if there are any known adverse health effects with the chemicals in the residue. Some foam agents can cause damage to the nervous system or vital organs, even with limited exposure. If working with an agent that carries this risk, you will need to use an air-purifying respirator. Regardless of the type of wet agent you are cleaning, the area should always be well-ventilated as a precaution against inhalation of mist or fumes while working.


Depending on the type of fire extinguisher used, it may appear that there is nothing much to clean. If this is the case, the fire extinguisher used may have been a clean agent fire extinguisher. Clean agents are electrically non-conductive, non-volatile, and leave no residue, which makes them ideal for use in areas with sensitive electronic equipment or other materials that might be damaged by water or wet chemicals.

There are two primary types of clean agents used in portable fire extinguishers today, those that contain carbon dioxide (CO2), and those that contain Halotron, an alternative to the older Halon-based extinguishers. While Halon-based fire extinguishers are still in use today, they are not as common as they once were due to the 1994 ban on Halon production in the U.S. in 1994 over environmental concerns.

While most of the gas for clean agent fire extinguishers dissipates into the atmosphere, it is still a good idea to clean any areas in which they were used to remove any particulates left behind by the flames themselves and to neutralize any smoky odors. This can be done simply by wiping down the affected area with a diluted degreaser.


Cleaning up after using a portable fire extinguisher can often be accomplished quickly and with surprisingly little expense. However, the job should not be considered complete until your fire extinguishers are placed back into service and ready for the next time you need them.

The National Fire Protection Association (NFPA) 10 Standard for Portable Fire Extinguishers requires that fire extinguishers to be recharged after each use, even if used only partially.

If you’ve recently used one or more of your fire extinguishers or have concerns regarding their condition, contact Koorsen today. Our team of experts is ready to help with the highest quality products, training, and service to meet all of your fire extinguisher needs.

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Topics: Fire Protection, 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.