This is the FIRE TRIANGLE. There are four elements that must be present for a fire to exist. There must be Oxygen to sustain combustion, Heat to raise the material to its ignition temperature, Fuel to support the combustion and a Chemical Reaction between the other three elements.
REMOVE ANY ONE OF THE FOUR ELEMENTS TO EXTINGUISH THE FIRE.
HOW TO USE FIRE EXTINGUISHER
TYPES OF FIRE EXTINGUISHERS
1. Water & Foam
Water & Foam fire extinguishers extinguish the fire by taking away the heat of the fire triangle. Foam agents also separate the oxygen element from the other elements.
Water extinguishers are for Class A fires only. They should not be used on Class B & C fires. The discharge stream could spread the flammable liquid in a Class B fire or could create a shock hazard on a Class C fire.
Foam extinguishers can be used on Class A & B fires only. They are not for use on Class C fires due to the shock hazard.
2. Carbon dioxide
Carbon dioxide fire extinguishers extinguish the fire by taking away the oxygen element of the fire triangle and also by removing the heat with a very cold discharge.
3. Dry chemical
Dry chemical fire extinguishers extinguish the fire primarily by interrupting the chemical reaction of the fire triangle.
Today's most widely used type of fire extinguisher is the multi-purpose dry chemical that is effective on Class A, B and C fires. This agent also works by creating a barrier between the oxygen element and the fuel element on Class A fires.
Ordinary dry chemical is for Class B & C fires only. It is important to use the correct extinguisher for the type of fuel! Using the incorrect agent can allow the fire to reignite after apparently being extinguished successfully.
4. Wet chemical
Wet chemical is a new agent that extinguishes the fire by removing the heat of the fire triangle and prevents reignition by creating a barrier between the oxygen and fuel element.
Wet chemical or Class K extinguishers were developed for modern, high-efficiency deep fat fryers in commercial cooking operations. Some may also be used on Class A fires in commercial kitchens.
5. Clean agent
Halogenated or Clean Agent extinguishers include the halon agents as well as the newer and less ozone depleting halo-carbon agents. They extinguish the fire by interrupting the chemical reaction of the fire triangle.
Clean agent extinguishers are primarily for Class B & C fires. Some larger clean agent extinguishers can be used on Class A, B and C fires.
6. Dry powder
Dry powder extinguishers are similar to dry chemical except that they extinguish the fire by separating the fuel from the oxygen element or by removing the heat element of the fire triangle.
However, dry powder extinguishers are for Class D or combustible metal fires, only. They are ineffective on all classes of fires.
7. Water mist
Water mist extinguishers are a recent development that extinguish the fire by taking away the heat element of the fire triangle. They are an alternative to the clean agent extinguishers where contamination is a concern.
Water mist extinguishers are primarily for Class A fires, although they are safe for use on Class C fires as well.
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