The LWF Blog

Fire Safety for Facilities Management Personnel – Fire extinguishing appliances – Part 218

September 11, 2023 11:22 am

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 217, LWF discussed fire extinguishing appliances, including the requirements of fire insurers. In part 218, we will talk about portable fire extinguishers, particularly water extinguishers.

The common media contained within a fire extinguisher may be one of four extinguishing agents, as follows:

  • Water
  • Foam
  • Powder
  • Carbon dioxide

Other agents in portable fire extinguishers are intended for particular applications and will be discussed later in this blog series.

Water fire extinguishers

A water fire extinguisher is intended for use on Class A fires, which are those involving typical combustibles like wood, paper, textiles etc.

A water fire extinguisher would not be appropriate for use on Class B fires, which involve flammable liquids or for using on live electrical equipment.

Water works to extinguish a fire by cooling the fuel source and a portable fire extinguisher can normally penetrate most normal fuel sources with the water reasonably well.

The most commonly-installed size of extinguisher contains 9 litres of water which, when pressurised by the extinguisher, discharges for around 1 minute. The reach of the extinguisher is approximately 6 metres. The extinguisher works by either releasing permanently stored pressure within the canister or from the generation of pressure upon operation as gas is released from an internal, pre-sealed gas cartridge.

A water fire extinguisher is relatively heavy (the 9 litre version weighs around 13 kg, or around 28 lbs) and so while they are classed as portable, some members of staff might find them difficult to carry and manipulate. Extinguishers of smaller capacity and less weight may be appropriate, some contain an additive like a wetting agent and might therefore be given the same rating as a 9 litre water extinguisher. They are commonly a 6 litre extinguisher and may be appropriate for installation in a building where the normal occupancy have been considered and a 9 litre extinguisher is deemed to be too heavy, although the short discharge time of the lesser amount of water/additive means that their effectiveness in the hands of untrained staff is debatable.

It should be noted that all staff should receive fire safety training and fire equipment training as a priority and any staff transferred from other bases should receive training at their new place of work. However, unless they were a firefighting professional, ensuring the full 6 litres of water/additive is delivered to the appropriate point of a fire in the very short time available could be a tough challenge.


In part 219 of this series, LWF will talk about foam portable fire extinguishers. 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 35 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.

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