The LWF Blog

Fire Engineering Design and Risk Assessment – Fire and Smoke Ventilation – Part 10

March 23, 2017 11:53 am

In the previous blog of this series for Architects and others in the construction industry, we began looking at how pressurisation is used as a method of fire and smoke ventilation, by raising the pressure of the area to be protected to a pressure greater than that of the surrounding spaces.


In Part 10, we will continue looking at pressurisation before talking about natural ventilation systems.The practical use of pressurisation in residential buildings is often to be found in pressurisation of the stair and corridor area, which negates the need for a vent. In a block of flats, leakage from the individual dwellings is often a design parameter which means that smoke does not enter the corridor. The downside of such a design, however, is that once the individual flats are occupied or sold, it is potentially difficult to control the vents within.


Another potential hazard is that if the entrance door of the flat of fire origin is left open to the corridor, then the pressure would quickly equalise, potentially this could mean that with the other flats at a lower pressure, it could force the smoke into those areas.


The requisite fans and power supplies for such a system are similar to those found in a depressurisation system, discussed earlier in this series, with the exception that the temperature rating of the fans can be ambient.Because of the particular requirements of a pressurisation system in order for it to be effective, it is important that careful consideration is given to the type and use of the intended building and its suitability.


Natural ventilation systems have some similarities with the pressurisation method, but also differ in that smoke is allowed to flow into the protected escape route with passive protection in that area forming the final layer of protection.


The four types of natural ventilation in current use include, the natural venting of a common corridor in a residential building via a smoke shaft; the natural venting of a common corridor in a residential building direct to outside air; the natural venting of a firefighting shaft and the natural ventilation via permanent openings from refuse rooms and basement lobbies.


In part 11 of this series we will begin with looking at residential buildings in terms of natural ventilation and the legislative documents which cover their use in England and Wales, Scotland and Northern Ireland. 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.

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