How a fire extinguisher works

Fire extinguishers are an integral part of dealing with fires, and an understanding of how a fire extinguisher works will enable you to be able to better use this equipment in case of an emergency. Before going into the details of how a fire extinguisher works, it is important to understand that there are a number of types of fire extinguishers and each one works in a different way. However, the basic working principle can be learnt for a fire extinguisher.

For a fire to sustain, it needs the following:

• Heat to sustain itself and propagate
• Fuel to keep burning and spread to new areas
• Oxygen that is central to combustion of fuel

Even if one of these is taken away, the fire cannot sustain and will die off. This is the basic principle on which fire extinguishers are built that help to extinguish a fire. Different types of fire extinguishers remove different components that require the fire to sustain, thereby extinguishing it.
The following are the three main types of fire extinguishers in use today, and their method of fire extinguishing is as follows –

• Water extinguishers: Water is one of the most commonly used fire extinguishing agent. Water fire extinguishers work by removing heat from the surface, thereby killing the fire. In water extinguishers, compressed air pushes water to come out of the tank to be sprayed on fire.
• Gas extinguishers (mainly carbon dioxide extinguishers): Carbon dioxide fire extinguishers contain high pressure carbon dioxide in the liquid form. When this gas is suddenly released on a fire, the gas expands by a huge amount, thereby reducing its temperature. In addition, carbon dioxide is heavier than air, so it settles down. This means that carbon dioxide fire extinguishers work by removing heat and also oxygen supply to the fire, and thus they are effective in extinguishing fires.
• Dry chemical extinguishers: These work by cutting off the fuel supply to the fire. When dry chemical powder is sprinkled around the fire, the powder tends to form a layer on top of the fuel and thus cuts it off from the fire. The powder being non-flammable, the fire doesn’t get the fuel to sustain itself and thus extinguishers.

There are several types of fire extinguishers and understanding how a fire extinguisher works will only help you use it more efficiently. For example, certain types of fire extinguishers should not be used in certain types of fires, and an understanding of the principle of working of different fire extinguishers will help you make the right decisions.