Types of Fire Extinguishers

A fire extinguisher can help save lives and prevent extensive property damage in the event of a fire. It’s smart to keep one in your home and is even required by law in some states. Learn about the different types of fire extinguishers, how they work and what to do in the event of a fire so you can be prepared.

There are five common groups of fire extinguishing agents, and each class of fire requires a different type of agent. The key is to select an extinguisher with an agent that can handle the expected type of fire while minimizing damage to sensitive equipment and other property.

Class A Fires: Ordinary combustibles, such as wood, paper, cloth, trash and plastics.

Class B Fires: Flammable liquids, including gasoline, oil, paint and flammable gases such as propane and butane.

In general, water-based extinguishers have a very low rate of discharge, making them best for minor fires that won’t spread rapidly and easily. They also leave behind very little residue, and are safe to use on energized electrical equipment.

For larger or more severe fires, halogenated agents (carbon tetrachloride and liquid chlorobromomethane) suppress fire by dispersing vapors and creating an oxygen-excluding blanket around the flames, preventing re-ignition. These are generally used on Class A, Class B and Class C fires, but be careful in electrical hazards because they can shock or harm people.

Dry powder (M28 or L2) extinguishers smother Class D fires by absorbing the burning metal swarf and creating a barrier that insulates the surface and stops the burn. They typically have a low-velocity applicator to avoid disrupting any fragile, finely divided burning materials and can be used on live electrical equipment because they don’t interfere with the circuitry.

Class D fires may also be managed with a hose-mounted suppressant such as a sodium bicarbonate (baking soda) firefighter, which works by displacing the air and cooling the fire, thereby cutting off its fuel source. This is an inexpensive option and can be effective on very small fires or in areas where water would be harmful, such as computer rooms.

Carbon Dioxide fire extinguishers emit a clean, dry gas that quickly displaces oxygen and has a short range, so it must be applied closely to the fire. They can be used on Class A and Class B fires and are very effective in confined spaces. They are not recommended for outdoor use or in locations where strong air currents could blow the gas away before it can be discharged. In addition, the high concentration of CO2 can cause frostbite and suffocation in humans if inhaled directly.

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