The LWF Blog
Fire Safety Engineering for Design – Foam Fire Suppression Systems – Part 268
January 5, 2026 9:51 amLWF’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 267, LWF began to discuss a different kind of fire suppression system to sprinklers – foam systems. In part 268, we continue to talk about how foam suppresses and extinguishes fire by looking at a particular type of foam – Synthetic Detergent.
Synthetic Detergent (SD)
SD foam works to suppress fire by creating a blanket of foam to smother fuel, block oxygen, cool surfaces and block flammable vapour release.
Synthetic detergent concentrate is a type of foam comprising a mixture of synthetic foaming agents with added stabilisers. The versatility of SD concentrates means that they can be used to create low, medium and high expansion foams. They are sometimes referred to as ‘high expansion foam concentrates’. They are capable of producing sufficient wetting for a class A solid combustible material fire.
SD concentrate foams tend to have fluidity and are able to flow around obstacles in order to achieve rapid knockdown of a fire. The downside of such an adaptable foam is that it can have low stability and quite rapid drainage times. This means they don’t offer a great deal of heat resistance and tend to dissipate fairly quickly. For instance, SD foams can offer little burnback resistance and capabilities at fuel surface sealing are limited.
The high-expansion foam made from SD concentrates can be used for a wide range of hazards, including vapour suppression of liquefied natural gas (LNG) and protection of stores of paper etc.
A standard ‘syndet’ foam would not be appropriate for use on water-soluble fuels.
Not all types of SD foams available can exhibit good dry chemical compatibility. It is possible to procure SD foams in various concentrations, but the most common are 1.5-2%. Low temperature grades are also available.
In part 269 of LWF’s series on fire engineering we will look at the composition and capabilities of film-forming fluoroprotein 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.