Fire Extinguisher Guide: Types, Use, and Safety

How does a fire extinguisher work
and how should it be used?
Any fire has three essential elements:
 Extreme heat
 Oxygen (or another type of gas)
 Fuel—the burning material
A fire stops burning when any one of these elements is removed. The
relationship between these factors is often visualized as a “fire triangle”
(pictured below). But while it’s the easiest to visualize, the fire triangle
has been largely replaced by the fire tetrahedron. The tetrahedron adds
one more element: chain reactions, which create a gaseous fuel that
sustains fires.

The “fire triangle” illustrates the elements needed for a fire to ignite.
Removing any one of these three elements stops the fire from burning.
Image source: Wikipedia.
Some extinguishing agents smother the fire, depriving it of oxygen.
Others cool the burning material, removing heat. All fire extinguishers
are similar in the sense that they deprive the fire of one or more of these
elements. But not all extinguishers are effective against the same fires.
Some can’t penetrate deeply enough to stop fires in ordinary
combustibles, for example, while others can’t stop fires in flammable
liquids—and can even spread the fire.

What are the types of fire
extinguishers and their uses?
Most fire extinguishers operate in a fashion similar to an aerosol can. The
tank contains compressed gas, pressurized liquid, or a combination of
the two with an added extinguishing agent. Squeezing the fire
extinguisher’s lever creates an opening that allows the compressed
material to escape through a nozzle or short hose.
But beyond those mechanical similarities, fire extinguishers vary widely.
There are at least eight types of fire extinguishers:
Carbon Dioxide (CO2)
Carbon dioxide extinguishers are Class B and Class C fire extinguishers.
They remove the oxygen from the fire triangle and infuse a cold
discharge to cool the fire. Unlike water or some other extinguishing
agents, CO2 does not conduct electricity, making it especially well-suited
for electrical (Class C) fires.

CO2 fire extinguishers, like this 5-pound model from Buckeye, feature a
large horn instead of a hose.
Water and Foam
These extinguishers employ foam agents to remove the heat from the
flames. The foam also covers the fuel in a blanket that deprives the fire of
oxygen. Water and foam extinguishers are used for Class A fires only.
Why? The water in these extinguishers can cause the flammable liquids
in Class B fires to spread or increase the shock hazard in a Class C
electrical fire.
Dry Chemical
Dry chemical fire extinguishers use multipurpose agents that extinguish
Class A, B, and C fires. This suitability for the most common fire types
makes these and other “Class ABC” fire extinguishers the go-to choice in
homes or offices.

A dry chemical ABC fire
extinguisher.
Wet Chemical
Wet chemical extinguishers remove the fire’s heat. The chemical
extinguishing agent also creates a barrier between oxygen and fuel.
Some wet chemical extinguishers can tame both Class K and Class A
fires.
Clean Agent/Halogenated