The LWF Blog

Fire Engineering for Healthcare Premises – Smoke – Part 38

June 1, 2021 7:56 am

In LWF’s blog series for healthcare professionals, our aim is to give information on best practice of fire safety in hospitals and other healthcare premises. In part 37 of Fire Engineering for Healthcare Premises, LWF talked about spill plumes and smoke reservoirs. Part 37 was published out of sequence, so you can read it by clicking here. In part 38, we discuss smoke curtains in more detail as well as beginning to look at smoke venting.

When designing a smoke and heat exhaustion ventilation system (SHEVS), it may be necessary to include features such as channelling screens or to block openings in a way that would not be feasible for day to day operations within the building. One way of approaching the necessity of closing off areas in a fire situation for smoke control is to install smoke curtains which operate when the smoke control system is activated.

Smoke curtains must be designed to operate reliably and safely and occupants must not be in danger of being struck by a curtain during deployment. It is obviously necessary for them to be able to withstand the predicted smoke temperatures during operation.

Curtains may be free-hanging and can be deflected (and not provide an effective seal) due to the buoyant pressures of hot gases contained to one side of the barrier or by air movement caused by the extraction system.

Smoke ventilation

A healthcare building may employ either natural or mechanical ventilation to remove smoke. Natural ventilation uses openings in the roof or side of the building for smoke to leave using its own natural buoyancy.

The vents will require opening when a fire is detected and several mechanisms are available, including servos activated by the smoke detection system, or fusible links which operate when they reach a sufficiently high temperature.

A mechanical smoke ventilation system uses fans and commonly, a network of ducts to extract the smoke. Some fans may be directly mounted on the roof of the building. Usually, smoke is extracted from a smoke reservoir, but extraction from slit vents across openings is also possible.

The potential for outside weather to affect a smoke ventilation system must be considered. Wind can blow smoke back into the building when a natural ventilation system is used if the potential for wind has not been mitigated. Smoke leaving the building must not be able to re-enter or to affect other buildings.

In Part 39 of LWF’s blog series, LWF will continue discussing the ventilation of smoke before looking at SHEVS. 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 LWF on freephone 0800 410 1130.

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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