The LWF Blog

Fire Engineering for Healthcare Premises – Fire Development – Part 12

December 7, 2020 12:11 pm

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 11 of Fire Engineering for Healthcare Premises, LWF looked at terms such as vitiated fires, flashover and backdraft. In part 12, we consider the effects of suppression, compartment fire modelling and cone calorimetry.

While fire and smoke suppression systems are designed to assist in a fire situation, they can also exhibit adverse side-effects when something goes wrong. The accidental discharge of an inert gas system in a closed room could suffocate the occupants; the accidental discharge of a sprinkler system may affect electrical systems adversely.

Halon systems are environmentally unfriendly and as a result, the production of halons is now banned by the Montreal Protocol. Their use in fire suppression systems is discontinued in all but the rarest circumstances – the Channel Tunnel being one situation in which a halon system is still in use. Halon systems can only be specified if they use recycled gases.

Hot smoke which is cooled by a water spray may lose buoyancy and allow the smoke layer to mix with the clear air beneath. This can cause poor visibility and breathing conditions in escape routes.

In compartment fire modelling, any strange or unexpected results require an adequate explanation from the user. For example, the ‘trench effect’ identified in the King’s Cross fire investigation was confirmed and supported by subsequent small and large-scale experiments.

Cone calorimetry is used to produce data on materials. A cone calorimeter is a device used for predicting real-time fire behaviour and can determine parameters such as ignition time, heat release rate, mass loss, and other properties relevant to fire characteristics. The heat release rate, for example, is calculated by knowing the percentage of oxygen consumed during combustion. Significant data (for example materials possessing notably high heats of combustion) may indicate a need for design review.

Where cables pass between compartments and through cavity barriers, adequate fire-stopping must be used to stop the passage of smoke and fire through the aperture, if a fire were to occur in one of the adjoined compartments.

The potential for cables themselves to contribute to a fire in a fire-safety engineered building must also be considered and the materials they are made of may contribute to this potential hazard.

In Part 13 of LWF’s blog series, LWF will begin to discuss the elements of smoke spread and control. 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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