The LWF Blog

Fire Safety Engineering for Design – Foam Fire Suppression Systems – Part 289

June 1, 2026 9:04 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 288, LWF began to consider the testing that should take place before a foam fire suppression system is put online. In part 289, we continue to discuss testing of these systems.

The parts of a system may be individually checked without a fully-working test, but ideally, the full system should be tested to ensure it works as intended.

Ensure foam proportioning is at the correct ratio, using the right ratio ensures the foam acts as intended. Tests to check proportioning are specified in EN 13565-2 and NFPA 11.

Any foam solution discharged during testing should be contained and disposed of by environmentally-sound means. A failure to do this can lead to contamination of groundwater, pollution of rivers and soil, cause harm to wildlife and has the potential for long-term damage.

After commissioning, the system should be tested at least once a year. If this is neglected, there is the potential for the system to fail in a fire situation.

Foam concentrate used in a foam fire suppression system should be sampled and analysed annually to ensure its key physical and chemical properties are within the limits established by the manufacturer.

The checked parameters should include:

• PH (could become too acidic or alkaline, indicating chemical breakdown or system corrosion)
• specific gravity/density (confirms solution has not been diluted or altered)
• sediment content (detects sludge or solids which may block pipework)
• refractive index (testing helps verify concentrate composition and consistency)
• viscosity (tests how easily the foam concentrate flows through the system)

The parameters do not directly affect or measure firefighting effectiveness, however, significant changes can indicate the formulation has deteriorated through contamination or other means or has chemically-degraded while stored. It is possible that the foam may no longer proportion correctly or generate stable firefighting foam when discharged in a fire emergency.

Annual testing helps to ensure that both the system and the foam produced by the system are working as originally tested and continue to be suitable for the purpose intended.

In part 290 of LWF’s series on fire engineering we will continue to discuss foam fire suppression with modern foam concentrates and premix foams. 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.