The LWF Blog

Fire Safety for Healthcare Premises – Venting of Basements – Part 61

February 12, 2019 11:20 am

In LWFs blog series for healthcare professionals, the aim is to give information on best practice of fire safety in hospitals and other healthcare premises. In part 60 of this series, the placement of fire hydrants in relation to hospital buildings was discussed. In part 61, we will look at the effects of smoke on basement levels and the use of venting.

A fire which starts in a basement or involves a basement level causes additional complications to a fire on any above ground level. The products of combustion – heat, smoke, airborn particles and other gases – naturally rise and the only escape they often find is stairways. The filling of stairways with hot smoke makes access difficult for the Fire Service. 

Venting of basement areas is therefore an important fire protection measure which can reduce the problem of smoke filling the stairway to basement levels by improving visibility and lowering the temperature.

Vents to open air mean that the smoke and heat can escape more easily and they can be used by the fire service to let cooler air into the basement as required. Smoke outlets to the open air should be provided from every basement storey except where it has a floor area of less than 200 m2 or where it is not more than 3 metres below the adjacent ground level.

The positioning of smoke outlets within the basement space should be considered in order for them to be effective. They should be positioned at a high level, be evenly distributed around the perimeter of the building and discharge into open air outside the building.

In each basement compartment or sub-compartment, the combined cross-sectional area of all smoke outlets should be not less than 2.5% of the floor area of that compartment or sub-compartment.

Where the smoke outlet terminates in a position that is not readily accessible, it must be kept unobstructed and covered with a metal grille or louvre to avoid it becoming covered or blocked accidentally, which would mean the smoke could not vent from that outlet.

Where the smoke outlet terminates in a position that is accessible, it should be covered with a suitably indicated panel or pavement light which can be broken out or opened at will.

Smoke outlets should not affect the use of escape routes and so planning in this regard will be necessary.

In part 62 of this series, LWF will consider the mechanical extraction of smoke from basement levels and the construction of outlet ducts and shafts, before beginning an overview of Firecode (HTM 05-03: Operational Provisions). 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.

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