The LWF Blog

Fire Engineering for Healthcare Premises – Smoke – Part 37

June 7, 2021 11:38 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 36 of Fire Engineering for Healthcare Premises, LWF considered ASET and RSET (Available vs Required Safe Egress Time). In part 37, we begin to discuss spill plumes and smoke reservoirs.

A spill plume is a rising plume of hot gases over a fire, but this is not the only place where a spill plume can be found and smoke can be diluted. Longer ‘line’ plumes can develop where smoke spills from under a balcony, looking much like an inverted waterfall, or past the top edge of an open window.

Spill plumes are commonly found in fire situations occurring in atria, shopping malls and other geometrically complicated buildings. Air can be entrained on one or two sides, dependent on whether the rising plume attaches to a vertical surface.

The presence of a spill plume affects the dilution of the smoke and therefore the sizing of any extract system. The plume width may be controlled by the use of channelling screens.

A smoke reservoir is an area at a high level in a building, commonly an atrium in healthcare buildings, designed to trap and hold the rising smoke of a fire. The holding of the smoke in the designed area helps to prevent the spread of smoke to other parts of the building.

A system can be designed to extract the smoke from the reservoir at a rate matching the smoke supply rate and in doing so, can indefinitely extend the ASET. The addition of such a system may be unnecessary if the time taken to fill the smoke reservoir provides an adequate ASET.

The reservoir design may be formed by the building’s structure at ceiling level and this can be further assisted by fixed or automatic smoke curtains. Fixed smoke curtains may be glazed, depending on the compatibility with expected smoke temperatures, allowing the upper part of the atrium to retain a design feature appearance while fulfilling the necessary requirements for a smoke reservoir.

In Part 38 of LWF’s blog series, LWF will discuss smoke curtains in more detail as well as beginning to look at smoke venting. 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.

NOTE: As Part 38 was published out of sequence, you can read it by clicking here.

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.