Different Types of Fire Extinguisher
Fire extinguishers work by removing one or more components of the fire triangle but if you use the wrong type, such as using a water based extinguisher on a chip pan fire, it can be ineffective and can do more harm than good, potentially causing immediate and explosive reactions. As seen in the diagram, In the UK there are 5 main types of fire extinguishers in use which are all colour coded for quick and easy identification and used for different classes of fire which we discussed here.
Water Extinguishers: Water is the most common type of fire extinguisher for Class A fires with most premises requiring either a water or foam extinguisher to be present. They do not contain harmful chemicals but unlike some of the other extinguisher types have a low firefighting rating, usually making them rather large and heavy. The water has a cooling effect on the fuel, causing the fuel to burn at a slower rate until the flames are eventually extinguished. There are actually 3 types of water extinguisher, Water, Water Spray and Water Mist, the difference being the type of nozzle. Water spray extinguishers have a spray nozzle that allows a greater surface area to be covered in a quicker time frame. Water mist extinguishers have a nozzle that releases tiny water particles which suffocate the fire and can reduce the feeling of heat for the person using the extinguisher.
Foam Extinguishers: Foam extinguishers are most common for Class B fires but as they are water based also work on Class A fires making them a good option for many environments. Foam extinguishers work by having a cooling effect on the fuel due to the water content with the foaming agent also creating a barrier between the flame and the fuel by floating on top of the burning liquid.
Dry Powder Extinguishers: Dry powder extinguishers are electrically non-conductive and work by creating a barrier between he fuel and source of oxygen. There are two types of dry powder extinguishers, the standard dry powder extinguisher and the specialist dry powder extinguisher. Standard dry powder extinguishers are more common than specialist and as seen in the above diagram can also be called ABC extinguishers because of their use for Class A, B and C fires. Specialist dry powder extinguishers work in the same way, the difference being that they are only for use with flammable metals. Due to the powder which can be inhaled, these types of extinguishers are not recommended for use in enclosed spaces and leave a residue that can be very difficult to clean up.
Carbon Dioxide Extinguishers: CO2 extinguishers can also be recognized by their slimline shape and are mainly used for electrical fires. They also have horns instead of nozzles which are not always frost free meaning they can get incredibly cold when in use. Carbon dioxide extinguishers work by displacing the oxygen in the air and suffocated the fire and are popular for use on electronics as they don’t harm the equipment and unlike some other extinguishers don’t leave a residue behind. However, if the source of the fire is not removed such as switching off the power supply or the materials are still very hot, once the CO2 gas has disappeared the fire may reignite.
Wet Chemical Extinguishers: Although wet chemical extinguishers can also be used on Class A fires they were designed for class F fires and work by creating a layer of foam on the surface of the burning oil or fat. This has a cooling effect and also prevents any further oxygen fueling the fire further.
How to Use a Fire Extinguisher
There are different instructions for each type of extinguisher (view a more detailed description of each here) and as with many things in life it is always best to let someone with appropriate training deal with the situation. However, in the case of an emergency there are some simple steps and something called the P.A.S.S method which can be followed
- Don’t attempt to fight a fire you don’t feel you are equipped to fight or that is too big. If you are unsure about your ability the safest option is to evacuate and let the fire services handle it
- The appropriate type of fire extinguisher is usually installed a short distance away from the risk but you should always check the coloured panel to ensure you are using the right one
- If there is a pressure gauge present check that the needle is in the green area
- Stand an appropriate distance away from the fire (depends on the type of fire extinguisher but on average it’s around 8 foot) and ensure you are near an escape route
- Use the P.A.S.S method
P – Pull the pin from the handle
A – Aim the hose at the base of the fire
S – Squeeze the lever/handles
S – Sweep the hose from side to side moving closer as the fire as the fire gets smaller
- If the flames flare up, stay at a safe distance and repeat the process but if the fire is not out by the time the extinguishing agent has been completely used, leave immediately and wait for the fire services to arrive