Water, Foam and Carbon Dioxide – Fire Extinguisher Training
It is common knowledge that fire extinguishers can put out fires when used correctly and it’s often the first thing to look for when a small fire has started. however it is often overlooked that there are different types of fire extinguishers for different types of fires and using the wrong type of fire extinguisher can actually make the situation worse. the following 3 types of fire extinguishers are specifically designed to combat certain types of fires.
1. Water
Water is the most widely used extinguisher agent and used for class a fires.
There are basically two types of water extinguisher:
(a) the gas CO2 cartridge operated extinguisher. When pierced by a plunger the gas adds pressure to the body of the extinguisher, thus expelling the water and producing a powerful jet.
(b) Stored Pressure extinguishers. here the main extinguisher body is constantly under pressure with dry air or nitrogen and is operated by opening the squeeze grip discharge valve.
These extinguishers are available with 2, 3, 6 or 9 litre capacity bodies and thus provide alternatives where weight and accessibility problems arise.
2. Foam
Foam can be used on class B fires where it will flow over the surface and smother the fire. the foam produced consists of small foam bubbles which have a very creamy consistency.
Another type of foam, a.F.F.F. (aqueous film forming foam) is becoming increasingly popular.
This can also be used on class a fires and it has better extinguishing properties than water, thus a lighter, smaller extinguisher can be provided that has the same extinguishing ability of a larger water extinguisher.
Foam extinguishers can be pressurised either by the CO2 gas cartridge method or by Stored Pressure.
These extinguishers come in the same capacities as that of water – 2, 3, 6 or 9 litres.
3. Carbon Dioxide
Designed specifically to deal with Class B, C and electrical fire risks. These extinguishers contain carbon dioxide gas at high pressure so that in effect, the gas contained within the cylinder is in liquid form. CO2 is an odourless liquid, relatively non-toxic, but it is an ‘asphyxiant’. When gas is released, so rapid is the rate of discharge that freezing up of the valve may occur.
The valve group contains a ‘piercer’ which, when operated, breaks the seal, allowing the gas to escape through the discharge horn. the horn is so designed to stop entrainment of the air, otherwise, the high velocity discharge would act like a blowtorch and increase the severity of the fire, a means of controlling the rate of discharge is normally provided.
CO2 is a non-conductor of electricity and this extinguisher can be used with safety on all fires of electrical origin with no danger of the operator receiving an electric shock.
They are also extremely useful in fires involving flammable liquids as the gas forms a blanket over the burning surface of the liquid, excluding the oxygen and smothering the fire.
These extinguishers come in 2 or 5 kg capacities.
