The LWF Blog

Fire Safety for Facilities Management Personnel – Fire Classification – Part 61

September 1, 2020 1:06 pm

Lawrence Webster Forrest (LWF) is a specialist fire engineering and fire risk management consultancy whose aim is to give information on best practice in fire safety for facilities management personnel through this blog series. In part 60, LWF looked at how fire can be extinguished. In part 61, we look at the classification of fires, so as to decide which are the most suitable extinguishing agents.

It’s a well-known fact that not all extinguishing agents are suitable for all fires. In order to make it easier to ascertain which extinguishing agent is suitable for which fire, types of fire have been classified according to the nature of the fuel.

Class A fires – are fires involving solid materials like paper, wood, textiles which form glowing embers as they burn
Class B fires – are fires involving flammable liquids or liquefiable solids
Class C fires – are fires involving flammable gases
Class D fires – are fires involving metals
Class F fires – are fires involving cooking materials such as fats and oils in cooking appliances

Electrical fires do not have a ‘letter class’, instead the symbol of an electric spark is displayed, and are fires caused by electrical equipment. The reason they are not classified in this way is that while electrical equipment may ignite a fire, it is rarely the major fuel source.

Commonly, where the power to the equipment is disconnected, a fire in electrical equipment will self-extinguish. Where the fire continues to burn it is usually because it has spread to other fuels, in which case the appropriate fire extinguisher for that fuel should be used. Where live electrical equipment is involved in a fire, an extinguisher should not be used as water expelled as a jet can conduct electricity and can result in an electric shock for the person attempting to put out the fire.

Most premises are not prone to Class C or D fires. Where a Class C fire does occur, the use of an extinguisher may be unwise as the fire can be due to a gas leak from a cylinder and the extinguishing of the flame may result in an explosion if no action is taken to prevent the leak from continuing to expel gas.

Class D fires require special extinguishing agents.

In part 62, LWF will continue to discuss fire classification, before considering the development and spread of a fire. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact LWF on freephone 0800 410 1130.

Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 25 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.

While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.