The LWF Blog
Facilities Management & Fire Safety – Fire Extinguishing Systems – Part 27September 28, 2017 11:25 am
LWF’s blog series, for those who work in facilities management or who have an interest in or responsibility for fire safety, has been looking at fixed fire-fighting systems and, in particular, gaseous systems for the last few issues. At the end of Part 26, we talked about wet chemical systems which are used mainly for the protection of deep fat fryers, either on a small or an industrial scale. In Part 27, we will discuss powder and aerosol systems.
In theory at least, a Powder System is suitable for both localised and total flooding uses, although in practice, powder systems are quite rarely seen in use and tend to be used mainly for localised risks. A powder system can be used for Class A (combustibles like wood, paper etc.) or Class B (fuelled by combustible liquids) fires.
Further information on Powder Systems can be gained through BS EN 12416-2:2001 – Fixed firefighting systems. Powder systems. Design, construction and maintenance.
An Aerosol System could be described as a combination of many of the other systems in some ways. The discharge of micron-sized particles of active matter – such as potassium carbonate – together with gas and water vapour forms an aerosol. The elements are generated by the electrical ignition of the solid particulate within the container. Historically, their use has been uncommon but in recent years, more information has become available which could enable increased usage. Potential applications include local application for plant and machinery or for the total application of a compartmented small area or room.
Further information on Aerosol Systems can be obtained from PD CEN/TR 15276-2:2009 – Fixed firefighting systems. Condensed aerosol extinguishing systems. Design, installation and maintenance.
The final fixed fire-fighting system we will look at is Oxygen Reduction Systems. An oxygen reduction system does not extinguish a fire but rather it makes it less likely that a fire will ignite and develop and in this way it is not a fire suppression system at all. The theory is that the oxygen level in a protected space is reduced through the introduction of nitrogen into the area. The oxygen is reduced to a level whereby it would not negate occasional occupation as the effect is similar to the lack of oxygen seen at a high altitude. Building occupants could therefore enter the room to perform tasks and leave unharmed, providing they do not have any medical conditions that would be exacerbated by lowered oxygen levels.
As the levels of oxygen must be kept low permanently, it would not be possible for people to work or inhabit the room on a longer-term basis.
Such systems are not frequently seen, partly because there are no current standards relating to their use, but British Standards are due to begin working on a draft in November 2017 and progress can be seen here – BS ISO 20338 Fixed firefighting systems – Oxygen reduction systems – Design, installation, planning and maintenance
Our next blog in this series will be Smoke Control – Part 1. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact Peter Gyere in the first instance on 0208 668 8663.
Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 25 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.