The LWF Blog

Fire Engineering for Healthcare Premises – Structural Fire Protection – Part 21

February 8, 2021 12:47 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 20 of Fire Engineering for Healthcare Premises, LWF discussed time-equivalent exposure and structural modelling. In part 21, we will talk about flames and radiation from windows and before beginning to consider fire detection and fire suppression.

It should be borne in mind when considering flames and radiation from windows in a healthcare building that the empirical nature of the equations for calculating height and projection of external flames means they can only be considered approximations, due to the large scatter in the data. They break-down if there are substantial heat losses to the façade, if external winds deflect the flame (reducing its length), if flames merge from more than one floor and if the burning rate is greater than expected, as can occur when fuel has a large surface area or where it is non-cellulosic with a higher volatility.

The calculation methods for radiation from windows include a number of caveats designed to reduce the number of trivial calculations.

In a fire situation, glass that is not fire-resistant is likely to break under flame impingement or at a relatively low temperature due to thermal shock and it is therefore most likely that radiation will be directly from the window space.

Smoke and fire detection systems are the first line of defence against fire in a healthcare environment.

In order to detect smoke in large areas and spaces, optical beam detectors are appropriate for use. Optical beam smoke detectors work on the principle of light obscuration. The photosensitive element perceives light produced by the transmitter in a normal condition which enables the receiver to be calibrated to a pre-set sensitivity level based on a percentage of total obscuration. There are two categories of optical beam smoke detector – projected and reflective, the type that is most appropriate will be dictated by the installation and environment conditions.

The response will vary depending upon fuel source for the fire and the properties of the resulting smoke. CFD simulation may be required in order to determine the optimum detector locations.

In Part 22 of LWF’s blog series, LWF will continue discussing fire detection and suppression by looking at heat detection in the first instance. 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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