The LWF Blog

Fire Engineering for Healthcare Premises – Fire Detection & Suppression – Part 47

August 9, 2021 12:02 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 46 of Fire Engineering for Healthcare Premises, LWF talked about fire detection and suppression. In part 47, we will continue to discuss fire detection and suppression systems and how they work.

The last blog in this series listed the types of fire detectors available for use in healthcare premises. It should be noted that in the simplest, lowest risk buildings, some systems may rely on manual alarms instead of automatic detectors, even though this would be highly unusual in recent times. A manual call-point can be activated by a person who sees a fire and although such call points are commonly seen, it is not usual for a fire detection system to only have manual alarms. Relying on an individual noticing a fire and raising the alarm can mean that the fire has already grown to a substantial size before the alarm is raised and evacuation can begin.

The number of detectors employed by a fire alarm system will vary depending on requirements, but the ultimate result is likely to be a compromise between the number of detectors possible and the level of finance available for the system.

Water suppression systems are cheap to run, once installed. Water is easily sourced and cheap and ideal in terms of its high specific heat capacity and high latent heat of vaporisation. In other words, it can work even in the high temperatures emitted by a fire.

Sprinkler systems are the most commonly used water suppression system. While practical experience of sprinkler systems has proven effectiveness, the complexity of the extinguishing mechanisms of water mean that only fairly rudimentary calculation methods exist to estimate sprinkler effectiveness.

There are various types of sprinkler system which have been created to address particular hazards. For instance, a water mist system works on a similar premise to a sprinkler system, but the water droplets are much smaller (producing a water mist). These systems extinguish fires by cooling gas, depleting sources of oxygen, diluting flammable vapours and wetting and cooling the surface of the fuel. They are best suited to use where sprinklers would be less effective, for example, hydrocarbon pool fires. They need to be used in a closed compartment for maximum impact.

However, a hydrocarbon fuel fire can best be extinguished by use of a fire-fighting foam rather than any kind of water extinguishing system. Foam systems spread over the fuel surface and suffocate a fire by depriving it of oxygen.

In Part 48 of LWF’s blog series, LWF will further discuss fire suppression systems, such as gaseous flooding systems. 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.