The LWF Blog

Fire Engineering Design and Risk Assessment – Fire and Smoke Ventilation – Part 2

January 26, 2017 11:58 am

In our blog series for architects and those involved in building planning and fire safety, we have most recently been looking at Fire and Smoke Ventilation. In Part 1, the reasons why smoke control might be necessary in a building were discussed, along with the objectives of such a system. We also established that there are two types of smoke control system – those which are designed to protect the area where the fire starts and those which are to protect any area beyond the fire area. In Part 2, we’re going to look at these in more detail.


In the case of systems which are designed to protect the area where a fire starts, there are two potential objectives:


To maintain a smoke-free layer for the escape routes – Such a system might be found in a shopping centre, for example. They work by maintaining a clear layer to enable people within the building safe egress without excessive smoke.


To dilute smoke building up in a space with fresh air so that visibility, tenability or temperature can be better controlled. Most often seen in a large area, they are useful when fires are small and where the normal internal conditions of the area, or wind pressures, might prohibit the formation of a stable smoke layer. This type of smoke control is most likely to be utilised in situations such as the removal of cold smoke from the area after the fire is out, or as an aid to firefighters, although they can aid means of escape in situations deemed suitable by the system design team.


Now, considering those systems which are designed to protect areas beyond the initial fire area, there are various factors upon which design and use can be based:


To effectively enclose an area with barriers to contain smoke, such as with the use of fire walls or smoke curtains.


To provide pressurisation or depressurisation as is necessary.


Smoke removal from the edge of a smoke reservoir, usually adopting a small ‘slit’ extract point, thereby preventing leakage from the reservoir.


To maintain a smoke-free layer on routes travelled by building occupants including escape routes.


To provide an opposed air-flow, the aim of which is to prevent smoke from spreading through large openings.


To dilute smoke which has seeped through into a protected area via vents or shafts within the building.


In Part 3 of this series, we’ll talk again about systems to protect an area where a fire starts, this time from a design perspective. 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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