A Full Overview : What Not to Use Foam Fire Extinguishers On

by Anna

Fire safety is of paramount importance in any environment, be it a residential, commercial, or industrial setting. Fire extinguishers are vital tools that can help mitigate the damage caused by fires. Among the various types of fire extinguishers available, foam fire extinguishers stand out due to their effectiveness in combating certain classes of fires. However, it’s essential to recognize that these extinguishers are not a one-size-fits-all solution. In this article, we delve into the limitations of foam fire extinguishers and explore what types of fires they should not be used on.


Understanding Foam Fire Extinguishers

Foam fire extinguishers, also known as AFFF (Aqueous Film-Forming Foam) extinguishers, are designed to combat Class A and Class B fires. Class A fires involve ordinary combustibles such as wood, paper, cloth, and plastics, while Class B fires encompass flammable liquids like gasoline, oil, and grease. The unique feature of foam extinguishers is their ability to create a foam barrier that suffocates the fire by sealing off the oxygen supply and simultaneously cooling the flames.


Limitations of Foam Fire Extinguishers

While foam fire extinguishers are highly effective in tackling Class A and Class B fires, they have limitations that must be understood to ensure proper fire response and safety. There are specific fire classes and scenarios for which foam extinguishers are not recommended and might even exacerbate the situation. Let’s explore some of these situations:

Electrical Fires (Class C)

Electrical fires involve live electrical equipment and circuits. Introducing water-based agents like foam to an electrical fire can be dangerous, as water conducts electricity. Foam fire extinguishers could lead to electrical shock or create a short circuit, escalating the danger. In the case of electrical fires, it’s essential to use fire extinguishers specifically designed for Class C fires, such as CO2 extinguishers, which displace oxygen and suffocate the fire without risking electrical shock.

Flammable Metal Fires (Class D)

Class D fires involve combustible metals such as magnesium, sodium, lithium, and potassium. These metals burn at extremely high temperatures and require specialized extinguishing agents that can withstand the intense heat. Using foam extinguishers on Class D fires is ineffective and can even result in a violent reaction, leading to the dispersal of burning metal fragments and the potential for more extensive damage. Sand, dry powder, or specific Class D fire extinguishing agents are appropriate for combating these fires.

Kitchen Grease Fires

Kitchen fires, often fueled by cooking oils and fats, fall under Class K fires. While foam extinguishers can combat Class B fires, they are not ideal for Class K fires. When foam comes into contact with hot cooking oil or grease, it can cause the oil to splash, potentially spreading the fire further. Instead, Class K-specific extinguishing agents, such as wet chemical extinguishers, are designed to effectively suppress these fires by creating a cooling and emulsifying effect on the burning fats.

Combustible Gases (Class E)

Class E fires involve combustible gases, which include propane, butane, and natural gas. Foam extinguishers are not suitable for these fires due to the volatile and gaseous nature of the fuel. Attempting to extinguish a gas fire with foam could lead to inadequate suppression and the potential for the fire to reignite. Fire extinguishers specifically designed for flammable gas fires, such as dry chemical extinguishers, are more appropriate in these situations.

Best Practices for Fire Extinguisher Use

Understanding the limitations of foam fire extinguishers is crucial for effective fire response. When confronted with a fire, it’s essential to follow these best practices:

Identify the Fire Class: Before attempting to use a fire extinguisher, ascertain the type of fire you’re dealing with. Look for the fire’s classification label, which indicates the type of fire the extinguisher is suitable for.

Evacuate if Necessary: If the fire is spreading rapidly, producing toxic smoke, or is beyond your control, evacuate the area immediately and alert emergency services.

Use the Correct Extinguisher: Select the appropriate fire extinguisher for the specific fire class. If you’re uncertain about the type of fire or the extinguisher to use, it’s better to evacuate and wait for professional assistance.

Stand at a Safe Distance: Maintain a safe distance from the fire and use the fire extinguisher according to the manufacturer’s instructions. Remember the “PASS” technique: Pull the pin, Aim the nozzle, Squeeze the handle, and Sweep from side to side.

Regular Maintenance: Ensure that fire extinguishers are regularly inspected, maintained, and charged as per manufacturer guidelines.


Foam fire extinguishers are valuable tools in combating Class A and Class B fires, as they effectively create a barrier to smother flames while cooling the fire’s heat source. However, it’s vital to recognize their limitations and avoid using them on Class C, Class D, and Class K fires, as well as combustible gas fires. Understanding the proper use of fire extinguishers and identifying the appropriate extinguisher for the fire class are critical steps in ensuring effective fire response and enhancing overall safety. When in doubt, always prioritize personal safety and evacuate the area before attempting to suppress the fire.


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