The LWF Blog

Fire Safety Engineering for Design – Foam Fire Suppression Systems – Part 286

May 11, 2026 8:41 am

LWF’s Fire Safety Engineering blog series is written for Architects, building designers and others in the construction industry to highlight and promote discussion on all topics around fire engineering. In part 285, LWF looked at high-expansion foam generators. In part 286, we discuss foam system design.

A foam fire suppression system is required to put out fires as quickly as possible. They work to apply sufficient foam by responding quickly to the fire signal and maintaining flow for long enough to put out the fire.

The duration of foam issue and the exact amount needed will vary depending on the situation. Conditions that effect those factors include the type of fuel burning, how the foam is delivered (through sprinklers, monitors, hoses etc.) and what type of foam concentrate is used.

NFPA 11 and EN 13565-2 both give recommended values for many common situations and these may be used during system design.

While the standards are very useful for more common situations, some hazards are more challenging, such as the potential for fires involving alcohol or polar solvents, both of which may break down the foam upon application. In such cases, the foam manufacturer should be consulted in order to adapt the application rate or the consulting fire engineer may recommend changes to another element of the fire protection system.

The basic steps for designing a foam fire protection system are as follows:

• Identify the type of flammable or combustible liquid involved
• Define the area that could potentially be affected by a fire
• Choose an appropriate foam type (e.g. FP, AFFF, AR-AFFF) and its mixing ratio
• Select the method and equipment for applying the foam (such as sprinklers, monitors, or nozzles)
• Determine the required foam application rate and application duration, based on relevant standards
• Calculate how many foam discharge devices are needed
• Work out the amount of foam concentrate required using calculation methods from the standards linked above (or the relevant standards of the country of operation)
• Determine the necessary water flow rate to support the system
• Identify the available water supply, including its volume, flow rate, and pressure
• Decide on the most effective way to supply both foam and water (e.g. fixed systems, mobile units, type of proportioning system)

In part 287 of LWF’s series on fire engineering we will discuss the components and materials of a foam fire suppression system. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.

Lawrence Webster Forrest has been working with their clients since 1986 to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact the LWF office on 0800 410 1130.

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.