During an emergency, there’s usually little time to reflect on the best course of action, and a potential fire hazard is a classic example of just such a scenario. That’s why it’s essential to prepare in advance for such eventualities. In essence, that means having the all correct fire extinguisher types in good working order, and in all the right places.
But do you actually know anything about the different types of fire extinguishers?
Water Fire Extinguishers
Water Fire Extinguishers are the ‘traditional’ approach to fire-fighting and work by cooling the surfaces heated by the fire, a process which inhibits its further progress.
Recognisable by their red colouring, these cylinders are designed to extinguish fires involving the more common combustible organic materials: for example cloth, coal, wood, paper and many plastics. Fires involving electrical equipment should not be tackled with water fire extinguishers – primarily because of the risk of electrocution.
This type of extinguisher is also an ineffective means of controlling fires where burning oil or fat is present – as is often the case with domestic kitchen fires, for example.
The best technique for using a water fire extinguisher is to direct the water jet towards the base of the rising flames whilst simultaneously moving the jet in a broad arc. It is essential to extinguish all flames in one area before moving on to the next.
Foam Fire Extinguishers
Foam Fire Extinguishers, which have a distinctive cream colouring, are effective on fires which involve solid materials or flammable liquids, such as paints and petroleum products – though foam is not a suitable choice for kitchen fires where oils and fats are present.
Foam can also be safely used on minor electrical fires, provided the extinguisher operator is at least one metre away from the flames. Foam extinguishers work by smothering the flames and thus preventing the fire from consuming any further flammable material.
This means the extinguisher is used in two different ways, according to the type of blaze: with solid materials, foam is projected towards the base of the fire in a broad arc – as with a water-based extinguisher, whereas with burning liquids, foam is carefully discharged so that it flows on to and across the contact surface of the flaming liquid.
Dry Powder Fire Extinguishers
Dry Powder Fire Extinguishers are coloured blue and are suitable for fires involving most burning liquids (excluding oil/fat kitchen fires). Dry powder extinguishers are also effective where organic solids are aflame, or where there are burning gases.
Though these are multi-purpose extinguishers, extreme care must be taken in certain circumstances: if used on electrical equipment fires, there is a risk of re-ignition because the powder may not penetrate every recess; a similar risk occurs with dense upholstery materials where powder fails to reach the seat of the blaze; and there is also a possible health risk from the powder itself, when discharged in a confined space.
The fire-retarding action of these types of fire extinguishers is mostly the result of the dry powder cooling the flames below the temperature at which combustion can take place. In use, the extinguisher should be discharged into the flame base, again in a wide arc, and the operator should ensure all flames are put out, even if this involves further applications to avoid re-ignition.
CO2 Fire Extinguishers
CO2 Fire Extinguishers are coloured black and are particularly effective against electrical fires, especially where commercial computer installations are involved. Operators should be aware that there is a danger of re-ignition with hot plastics, because flames are not cooled by any significant amount.
Instead, carbon dioxide extinguishers function by displacing the oxygen content in the atmosphere and thereby starving the fire of an essential component for combustion. When fire fighting, the CO2 jet should be applied to the flame base and then swept across from side to side.
Once applied to the flames, the CO2 is likely to disperse quite quickly, which means oxygen is soon restored to the fire, posing a real risk of further re-ignition.
Wet Chemical Fire Extinguishers
Wet Chemical Fire Extinguishers, coloured a distinctive yellow, are designed to combat fires involving typical kitchen materials such as a variety of fats and cooking oils, though not petroleum-based fires. Wet chemical extinguishers apply a fine mist over the flames.
This has some cooling effect but also causes a reaction which produces a foamy residue on top of the burning material, smothering the fire and reducing the danger of splashing material causing any further problems. The operator should ensure the chemical material is gently discharged over the fire so that the entire surface develops a foam-like appearance.
In addition, with these types of fire extinguishers the full contents of the cylinder should always be deployed to guard against the risk of reignition.
Proceed with caution
If the worst should happen, don’t try to tackle a fire unless you are certain you will not be in danger – which includes having an accessible escape route – and remember that different colour codings are used to identify the different types of fire extinguishers.
In addition, it’s essential to use the correct fire extinguisher types specifically designed to combat the fire hazard you’re faced with, otherwise there is a chance you might just make matters worse.