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Fire Engineering for Healthcare Premises – Structural Fire Protection – Part 22

February 15, 2021 12:32 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 21 of Fire Engineering for Healthcare Premises, LWF discussed flames and radiation from windows, before beginning to consider fire detection and fire suppression. In part 22, we will continue discussing fire detection and suppression by looking at heat detection in the first instance.

A heat detection system is one which is often used in property protection situations. It is designed to trigger when an element within the detector is heated to a certain level by a fire in the vicinity. Heat detection systems are also most useful in situations where a smoke detector is not able to function efficiently due to particulate matter, such as excessive dust and other contaminants which may be present in the air. A smoke detector is most frequently used where it is possible, because when life safety is the aim, achieving a safe evacuation in a smoke-free atmosphere is key.

Heat detectors are characterised by the response time index (RTI). A lower RTI means a faster response time, but this can also make the detector more prone to unwanted activations.

Radiation detectors must be calibrated so that the sensor is matched to hazardous and normal environments.

Delays can be experienced in operation of a detection device designed to trigger a sprinkler system, despite the hot gas temperature having equalled the nominal operating temperature. Various factors can affect the detection time, including heat conduction to the sprinkler pipes, sprinkler orientation, airflow detection and the latent heat of fusion for solder links.

The placement of detectors within a space is an important consideration and should be based on the earliest possible detection time, without increasing the potential for false alarms. At the start of a fire, the heat release rate (HRR) is low and therefore the normal air movement in the space will dominate the initial movement of smoke and hot gases. When fires are detected at this stage, there is a reduced risk of fire growth.

Computational Fluid Dynamics (CFD) software may be used in environments which are geometrically complicated, or where the pre-fire air flow is complex.

In Part 23 of LWF’s blog series, LWF will discuss sprinkler systems for healthcare premises. 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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