The LWF Blog

Fire Engineering for Healthcare Premises – Fire Detection & Suppression – Part 49

August 24, 2021 9:25 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 48 of Fire Engineering for Healthcare Premises, LWF discussed fire suppression systems, such as gaseous flooding systems like Halon, and how they work to extinguish fire in different circumstances. In part 49, we begin to look at Smoke Detection.

Smoke detectors are an essential part of a fire alarm system that are placed to sense the presence of airborne particulates, although they may work chemically by means of measuring gases such as carbon monoxide. Once activated, the detector sends a signal to the fire alarm panel and, in large and complex buildings such as hospitals, the fire alarm system will indicate the area in which the fire signal was triggered.

False alarms can be indicated when other airborne particulates than smoke are present, e.g. an excess of dust, steam or other elements related to the environment in which they are situated.

Ionisation detectors are best at detecting flaming fires. They work through responding to a change in electrical current through an ionisation chamber in the presence of smoke particles. The change is proportional to the size and amount of particles.

An optical detector is designed to measure the attenuation of a light beam interrupted by smoke, or light which has been scattered by smoke particles. An optical detector is usually best at detecting smouldering fire types.

Detection sensors can be incorporated into an integrated unit, which may include a sounder, or it can be situated remotely when using an aspirated system, whereby the air is drawn into pipes from the sensing point to the detector unit.

Optical and ionisation detectors respond differently to smoke from different fuel sources. Smoke tests, such as the cone calorimeter, cannot always accurately predict the response of a detector in-situ, because the detector may respond to properties measured under different conditions.

The assessment of a healthcare building and the various environments contained within will steer the choice of detector for an alarm system to ensure the best possible detection with the lowest chances of repeated false alarms. It is important that the most appropriate detectors and sensors are employed for the environment.

In Part 50 of LWF’s blog series, LWF will discuss sprinklers and the common types of systems that can be employed to suppress fire. 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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