We all know fire extinguishers are designed to help contain and extinguish fires, but it’s important to note there are different types of fire extinguishers. Though each extinguisher is typically red in the United States, they’re designed to handle different types of fires.

Fire Classes

There are 5 fire classes – A (Solid Combustibles), B (Flammable Liquids and Gas), C (Energized Electrical Equipment), D (Combustible Metals), and K (Oils and Fats). Each type of fire can be extinguished by different extinguishers. Here are the most common types of fire extinguishers on the market.

1. Water

Air-pressurized water can be used on class A fires. This extinguishing agent is cheap, but can’t be used on electrical, oil, liquid, or chemical fires. Water conducts electricity and doesn’t mix well with oils and other chemicals, so it’ll end up exacerbating any other type of fire.

2. Dry Powder

Dry-powder fire extinguishers are among the most common in the U.S. The specific chemical used can include monoammonium phosphate, sodium bicarbonate, potassium bicarbonate, and potassium chloride.

These are mostly used for class B and C fires, though they can be effective on class A fires as well. Dry powder extinguishers smother the fire, creating a barrier that robs it of oxygen, heat, and fuel.

3. Foam

Foam fire extinguishers use a foam made of agents, such as flouro-tensides, which form a crust on top of the flame that deoxygenates and extinguishes the flame. Typical foam extinguishers can be used on class A and B fires, while some can also be used on some class D fires.

Class D fire-suppressing agents include sodium chloride, graphite, and sodium carbonate. Most class D nozzles are also designed to be low pressure so as to gently lay the suppressant on the fire and not spread it.

Foam fire extinguishers shouldn’t be used on electrical fires as many foams conduct electricity, and they could make things worse.

4. Carbon Dioxide

CO2 fire extinguishers can be used on class C electrical fires. The carbon dioxide displaces oxygen and doesn’t leave any residue after discharge. This allows electronic fires to be isolated and extinguished without damaging the rest of the parts.

Carbon dioxide fire extinguishers can also be used on class A and B fires, though they should only be used in a well-ventilated space. When used in a confined space, the risk of explosion and death is heavily increased.

5. Wet Chemical

Wet chemical extinguishers are specially designed for class K fires. These extinguishers use potassium acetate, carbonate, or citrate to form a soapy foam blanket over cooking oil and cooling it below its ignition temperature.

Some wet chemical extinguishers can be used on class A, B, and C fires as well.
Fire extinguishers look the same, but they’re filled with different retardants meant for different uses. Recognizing the difference is important when working on a hazardous job site. Each extinguisher is labeled with a pictogram and/or geometric symbol designating what class of fires it extinguishes.

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Imagery courtesy of A1 Fire Sprinklers