Generally, fire extinguishers can be split into three types: pressurised water, carbon dioxide and dry chemical fire extinguishers. Fire is caused by a combination of oxygen, heat and fuel, and various extinguishers work against these three key catalysts in different ways to fight fire. Examining the different types of fire extinguishers that are present in schools is vital to maintaining optimum fire safety.
Classes of Fire
The different classes of fire that can be fought are listed on an extinguisher. Familiarising yourself with these classes is important to safe usage of fire extinguishers. "Class A" fires are fires started from common materials such as cloth, paper or wood. "Class B" fires are started by flammable liquids, solvents or gasses. "Class C" fires are electrical in nature, usually caused by things like fuse boxes and motors. "Class D" fires involve combustible metals such as magnesium, potassium and sodium, and "Class K" fires involve grease and cooking equipment. Most schools need to have a fire extinguisher that can fight size two "Class A" fires and size 10 "Class B" or "Class C" fires. The sizes are merely used for testing, and in cases like "Class B" (liquid) fires, the size refers to the amount of flammable fluid fuelling the fire in litres. A standard, dry chemical extinguisher is suitable for this purpose, and will be used by most schools. Some schools may also have other types of extinguishers.
Carbon dioxide fire extinguishers work by removing the oxygen supply from the vicinity of the fire. These fire extinguishers are best suited for areas with electrical equipment, because they do no damage and leave no residue. These fire extinguishers have a hard, black horn which is pointed at the fire before the gas is released. The extinguisher fires a white mist. There is no pressure gauge on these extinguishers. Carbon dioxide fire extinguishers can be used on electrical fires and gas fires.
Chemical fire extinguishers work by disrupting the chemical reaction that takes place to allow fire to exist. These fire extinguishers are becoming increasingly common because they are capable of fighting many of the different types of fire. Chemical fire extinguishers can be used to fight fires made by common flammable materials such as paper and wood, electrical fires, and any fire resulting from a solvent or a gas. These fire extinguishers sometimes have a hose, and will contain a pressure gauge. Dry chemical fire extinguishers used in schools are technically referred to as multipurpose dry chemical extinguishers, to differentiate from regular dry chemical extinguishers, which use sodium bicarbonate and are often found in kitchens and garages.
Pressurised water fire extinguishers are mainly suited for fires started by ordinary combustibles such as paper, wood, cloth and rubber. Pressurised water fire extinguishers are only useful for these "Class A" fires, and as such are being phased out of many learning establishments due to their limitations. Pressurised water fire extinguishers will include a gauge to help identify the pressure present inside them.