The LWF Blog

Fire Safety for Facilities Management Personnel – Fire extinguishing appliances – Part 223

October 16, 2023 11:06 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 222, LWF considered some of the other agents used in fire extinguishers, some in current use and some in past years. In part 223, we discuss the agents used in Class F extinguishers before looking at the relevant standards.

A Class F extinguisher usually contains a saponification agent designed to effectively transform flammable oil into a soap. The extinguisher will discharge relatively slowly in order to prevent splashing of the liquid which may lead to fire spread.

This type of extinguisher is often seen in a large commercial kitchen.

Special extinguishing agents are also used for Class D fires which involve combustible metals.

Consideration and performance requirements for fire extinguishers are given in BS EN 3, which comprises 10 parts. All parts are accessible from the BS EN 3 landing page on the British Standards Institute website.

Extinguishers which are manufactured in accordance with the standard, above, must be predominantly red, with an area no more than 10% of the overall area being coloured to indicate the contents of the extinguisher. Prior to 2019, BS 7863 indicated that in the UK, between 3 and 5 per cent of the extinguisher body should indicate the contents with a colour code. However, the publication of BS 5306-10:2019 and withdrawal of BS 7863 means that the European standard applies.

The colours for each agent are as follows:

Red – Water (both spray and mist)

Blue – Dry powder

Cream – Foam

Black – Carbon dioxide (CO2)

Yellow – Wet chemical

It may be necessary to look at all areas of the fire extinguisher to determine the contents as different manufacturers place the indication in varying areas.

Until 1997, it was permitted under European Standards to colour the entire extinguisher to indicate contents. Most manufacturers preferred to stay with the predominantly red extinguisher body as it was most familiar to the users.

BS EN 3 is a standard for use by manufacturers of extinguishers and is not aimed at the end user. This means that there is a variety of designs of extinguisher available and currently situated in buildings in the UK.  Some manufacturers even produce stainless steel extinguishers with a colour marking on to indicate contents and this is legal, although any design not complying with BS EN 3 will not be eligible for certification, e.g. Kitemarking by the BSI.

British Approvals for Fire Equipment (BAFE) produces a list of extinguishers which have been independently tested in accordance with BS EN 3. The Loss Prevention Certification Board (LPCB) also publish a list of tested fire extinguishers.

In part 224 of this series, LWF will begin to look at the siting of 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.

Share this post