There are a number of different extinguishing agents on the market, developed and designed to extinguish different types of fire. Fire are classified according to the combustible material involved.
Classes of Fire
Class A fires - are fires involving organic solids like paper, wood etc, as well as soft furnishings, fabric, textiles
Class B fires - are fires involving flammable liquids like petrol, oil or paints
Class C fires - are fires involving flammable gases
Class F fires - are fires involving cooking oil and deep fat fryers
Electrical equipment, like computers, does not fit in to any of the above classifications but has also been considered in this article.
It is essential to know which extinguishing agent should be used on which class of fire.
Types of Extinguishers
are good for tackling fires involving burning paper, wood and soft furnishings, as the water soaks into the materials (Class A fires). This type of extinguisher does not leave a residue , but does have a comparatively low rating. Due to this factor water extinguishers are larger and heavier to overcome their lacking in fire fighting power. It is important to remember that water is a electrolyte and conducts electricity. Care must therefore be taken with regards to accidental use on mains power. These problems can, however be overcome by installing water extinguishers with additive. This type of extinguisher has a higher fire rating, which therefore reduces the weight of the extinguisher and removes the risk of self-electrocution.
are suitable for flammable liquids and areas where soft furnishings and carpets are present (Class A and B fires). Foam extinguishers are safe to use with regards to electrical risk. This type of extinguisher usually contains additives which are carcinogenic, making the cleaning process of the premises after the vent of a fire more problematic.
CO2 (Carbon Dioxide) Extinguishers
contain only pressurised CO2 gas and leave no residue. This type of extinguisher is suitable for use on fires involving burning liquids (Class B fires), but is also an excellent solution for quenching fires involving computer equipment and other electrical appliances , as it does not cause damage to the electrical items and does not cause the system to short circuit. It is important to remember that when using CO2 extinguishers there is a possibility that once the gas has floated away the fire may reignite if the source of the fire is not removed (eg switching off the power supply). Please be aware that CO2 extinguishers that are not fitted with double-lined swivel horns may cause your fingers to freeze to the horn during the deployment of the CO2 gas.
also called ABC extinguishers, or dry powder extinguishers are suited to fight class A,B and C fires. Powder extinguishers have a good fire fighting capacity, but this agent does not soak into materials and does not have a cooling effect on the fire. This could result in the fire reigniting, if it is not properly extinguished. Care must be taken when using powder extinguishers and they should not be used in small confined spaces where there is a risk of inhalation of the powder.
Wet Chemical fire extinguishers
are suitable for use with fires involving burning oil and deep fat fryers (Class F fires). These extinguishers come with a special application lance which lays a cooling layer of foam on top of the burning oil. Alternatively a fire blanket can be placed over the pan containing the burning oil. The pan should then be left to cool down. NEVER carry the pan outside or lift the fire blanket after a short period of time to inspect the burning oil as introducing oxygen through this action could reignite the fire. NEVER use pressurised water, powder or foam extinguisher on fires involving burning oils as the pressurised jet will cause the burning oil to be carried out of the pan onto surrounding surfaces causing more damage and a larger fire to tackle.