The LWF Blog
Fire Engineering Design and Risk Assessment – Foam Systems – Part 2May 10, 2018 9:47 am
In LWF’s Fire Engineering blog series for Architects and others in the building design business, we have been looking at methods of fire suppression. In part 1, we looked at the suitability of foam systems for distinct kinds of potential fires. In part 2, we give an overview of the various types of foam typically available.
Each type of foam concentrate can be performance classified with three properties in mind. These are speed, heat resistance and fuel pick-up.
Protein foam has poor speed, poor fuel pick-up and excellent heat resistance. It is normally made with hydrolysed protein (animal protein concentrate) and produces a stiff foam which must be aspirated before use. Overall, it has poor firefighting properties.
Fluoroprotein foam exhibits fair speed response to fire, excellent heat resistance and good fuel pick-up (good fuel pick-up indicates low fuel pick-up). Just like standard protein foam, the fluoroprotein foam must be aspirated before use. It is a protein foam made with fluorochemical additives which flows easily.
Film-forming Fluoroprotein foam has a good standard in speed, heat resistance and fuel pick-up. While it can be used at its most effective when aspirated, it can also be used un-aspirated on spill fires.
Aqueous film-forming foam has excellent speed, fair heat resistance and good fuel pick-up. It is a synthetic foam made with fluorochemical surfactants. As the word aqueous indicates, it is designed to release an aqueous film which flows ahead of the foam giving the excellent speed indicated. The advantage of speed is slightly offset by the inability to produce a durable foam blanket effect. It can be used effectively in both aspirated and unaspirated forms and delivered through any water delivery nozzle, including through sprinklers.
Alcohol-resistant foam is able to produce good speed, excellent heat resistance and good fuel pick-up. They are used on fires involving foam-destructive flammable liquids which absorb water, such as alcohols and methanol. The film produced is polymeric which protects the water in the foam bubbles. The majority of available foams have an AR version. AR foams have a much higher viscosity than normal foams and so care must be taken by designers when considering proportioner performance.
In part 3 of this series, LWF will continue the overview of available foams for firefighting with Synthetic/high-expansion foams, Class A foam and Fluorine-free foams before looking at foam proportioning. 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 for over 25 years to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact Peter Gyere on 020 8668 8663.
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.