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As one brand used to famously advertise, “the right tool for the right job” can make all the difference in the world. When talking about fires, which are essentially chemical reactions gone amuck, the right extinguisher can be the only way to suppress a fire or keep it from spreading. Using the wrong type of extinguisher will have little to no effect, and can even make the fire worse.

To help make the right decision when a fire occurs on a job site — or anywhere else, for that matter — make sure to follow the standard extinguisher class recommendations for the type of fire.

Types of Fires

Almost all fires may look the same, but they can be a very different beast depending on the conditions that started it and the material fueling it. The classes of fire are as follows:

  • A — Dry, solid combustibles like wood, trash, carpeting, melting plastics and nearly any other everyday materials that have a solid form
  • B — Flammable liquids or gases like gasoline, or natural gas.
  • C — Fires created from an electrical source, regardless of whether they have spread to other materials. Electrical fires should have the power source shut down as quickly as possible to eliminate risk of electrocution.
  • D — Burning metals like magnesium or titanium. Generally, solid metals are not combustible, but powdered forms like metal shavings are. Class D fires are largely uncommon outside of specific industrial settings.
  • K — Fires started from cooking materials like oil or fat.


Types of Extinguishing Agents

The reason different extinguishers are needed for different fires stems from the agent used to suppress the fire. Check the label to make sure your extinguisher can be effective against the fire class in question.

Here are the most common extinguishing agents:


Water is suitable for stopping most class A fires if caught early. Using water is dangerous for class B fires since it spreads the burning agent out, and water used on class C fires would send electricity back towards the person operating the extinguisher.

Carbon Dioxide

CO2 extinguishers smother the fire by choking off the oxygen it needs to fuel the chemical reaction. CO2 can be effective for class B and class C but not class A, since CO2 on solid materials is ineffective. Using a CO2 extinguisher in a small space could suffocate the operator, so exercise discretion

Dry Powder

Newer monoammonium phosphate extinguishers are effective against class A, B and C fires, making them commonly seen in all settings. Other dry agents are effective against various types of other fires, such as class B and class C only.


Foam fire suppression agents use many chemicals suitable for different fire classes. These extinguishers are generally used in particular professional settings. For example, FFFP foam is used in motorsports, Arctic Fire foam is used in the steel industry and Cold Fire foam is used by emergency services.

Best General Safety Practices

In general, contractors and other people on the job site should have access to an extinguisher that can handle class A, B and C fires. Often known as “triclass” extinguishers, the pale yellow dry chemical agent is moderately corrosive, so it should be sprayed with care around other people.

Everyone involved should know how to operate the extinguisher and trained to recognize different types of fires. Extinguishers should be located in clearly marked spots on site or in easily accessible locations. If a fire has spread to the ceiling, has started putting out lots of smoke or people are in an area where escape would be difficult, the first priority should be to evacuate.

Every extinguisher must be periodically inspected for damage and recharged. Always be prepared for a fire situation and do not take the possibility lightly. Taking these precautions lowers the risk of fire spreading on a job and can easily save someone’s life.