Fire Extinguisher Guide: What to Use, and When

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Understanding how to use a fire extinguisher is an important part of staying safe. Most people don’t realize that there is more than one type of fire extinguisher and each type has a specific purpose for keeping people and property safe.

The first thing people should know when it comes to proper fire extinguisher use is that there are different types of fires, and not every extinguisher works for each one. The basic types of fires are:

  • Class A fires: Ordinary combustibles
  • Class B fires: Flammable gas and liquid
  • Class C fires: Electrical
  • Class D fires: Metal
  • Class K (also known as Class F): Kitchen fires (cooking oils, fats)

Take a look at the most common types of fire extinguishers and where you would likely use them:

Carbon dioxide - Class B and Class C fires

These fire extinguishers work by essentially removing the oxygen from the fire and releasing a cool discharge to take away the heat element.

Water - Class A fires only

These extinguish the fires by removing the oxygen element to put out the fire. They utilize the cooling, soaking, and penetrating effect of a stream of water to put out the fire. They are inexpensive to maintain, and leave no special chemical residue when used. These are pretty common but should only be used for Class A fires as they can actually make flames worse in other types.

Foam - Class A fires or Class B fires

Foam works by cooling the fire and coating the fuel, preventing its contact with oxygen, which in turn suppresses the fire. Class A foams lower the surface tension of the water, assisting in the wetting and saturation of fuels. Class B foams are designed to contain explosive vapors produced by flammable liquids.

Dry chemical - Class A, Class B and Class C fires – multipurpose, Class B and Class C fires – regular

The most commonly used type of fire extinguisher is the multipurpose dry chemical one. It can be used on three types of fires, and is especially effective when it comes to building a barrier between fuel and oxygen elements in Class A fires. The way that these extinguishers operate on most fires is by disrupting the chemical makeup of the fire triangle.

There is also an ordinary dry chemical extinguisher and it is only for use on Class B and Class C fires.

Wet chemical - Class K fires

This is relatively new fire extinguisher technology and works by removing the heat from the fire triangle and making it difficult for a fire to reignite. The most common place you would find a wet chemical extinguisher is in a commercial kitchen (usually stationed near the deep fat fryers).

Clean agent or Halogenated - Class B and Class C fires (some larger models work on Class A too)

This extinguisher uses halon and/or haloncarbon agents to disrupt the chemical reaction of the fire triangle. These extinguishers are recommended for use when sensitive electrical equipment could be damaged by the extinguishing agents in other types.

Dry powder - Class D fires

Similar to dry chemical extinguishers, they separate oxygen and the fuel source and remove the heat of the fire triangle. These extinguishers are designed for Class D fires (combustible metals) ONLY though and will not work on other fires.

Water mist - Class A fires

This newer fire extinguisher technology is less of a chemical concern than clean agent types since water is used instead. They take the heat element away from the fire triangle.

Cartridge operated dry chemical - Class A, Class B and Class C fires – multipurpose, Class B and Class C fires – regular

These fire extinguishers disrupt the chemical reaction of the fire triangle, like stored-pressure dry chemical extinguishers, but operate differently. The dry chemical is stored in the non-pressurized cylinder while the propellant is stored in a separate cartridge on the side of the unit. Their simple design, heavy-duty construction, and suitability for harsh environments make them ideal solutions for construction sites and heavy-equipment. The multipurpose models are approved for Class A, Class B, and Class C fires.

Fast flow - Class A, Class B and Class C fires – multipurpose

These extinguishers have a faster flow rate (which means they expel a higher volume of agent in less time) and lower UL rating than conventional fire extinguishers. Fast flow extinguishers are required in locations containing pressurized flammable liquids and pressurized flammable gas and areas with three-dimensional class B hazards.

The first step to fire safety is understanding the best way to combat each fire type. Based on where you plan to use the extinguisher, and for what purpose, use the list above to pick out the one that best fits your safety needs.

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