The LWF Blog

Fire Safety for Facilities Management Personnel – Fire Classification – Part 62

September 7, 2020 12:04 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 61, LWF looked at the classification of fires, so as to decide which are the most suitable extinguishing agents. In part 62, we will continue to discuss fire classification, before discussing the development and spread of fire.

Class F fires are those which involve cooking media – vegetable and animal oils and fats used in cooking appliances. This classification was created when it was acknowledged that all extinguishing agents used for Class B fires (those involving liquids or liquefiable solids) were not necessarily effective or suitable for use on fires involving cooking oil.

BS EN 3-7:2004+A1:2007 – Portable fire extinguishers. Characteristics, performance requirements and test methods provides a specification for portable fire extinguishers suitable for use with Class F fires.

It should be noted that other methods of extinguishing grease, oil and fat fires than extinguishers are available and should be considered prior to a fire extinguisher, if you are not sure the fire extinguisher is appropriate. Water should never be used on a fat or oil fire and nor should water-based extinguishers.

 

How fire develops and spreads

When a fire ignites in an enclosed area (as opposed to outdoors), the development can be very rapid. While mathematically, the development can almost be described as exponential, on a simple basis, it can be assumed that the fire is able to double in size in only a matter of a few minutes. Such sudden development is outside the experience of most non-professionals, as their experience of fire will mainly relate to fires outdoors, such as a bonfire.

Historically, the ability of fire to grow indoors at such a rapid rate has led to multiple-fatality deaths at various sites in the UK, notably Woolworths in Manchester in the late 1970s and the Bradford football stadium in 1985.

Fire develops and spreads through the transfer of heat from the flames by conduction, convection and radiation. Conduction can happen when a poorly insulted element of construction is in place, e.g. a metal fire shutter. Fire spread within a building can be mainly attributed to convection and radiation, however.

In part 63, LWF will continue looking at how fire develops inside buildings. 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.