The LWF Blog
Fire Safety for Facilities Management Personnel – Emergency Wayfinding Systems – Part 175November 7, 2022 12:28 pm
Lawrence Webster Forrest (LWF) is a specialist fire engineering and fire risk management consultancy whose aim is to give information on best practice in fire safety for facilities management personnel through this blog series. In part 174, discussed emergency wayfinding systems and began to look at directional sounders. In part 175, we continue talking about directional sounders.
The sound made by a directional sounder is what is commonly referred to as ‘white noise’. The electronic sounder produces a broadband sound covering the most audible frequency ranges of the human ear, between 20 Hz to 20 KHz. Broadband sound usage means people can locate the sounder much more easily than the restricted bandwidth emitted by fire alarm sounders.
The directional sounders are placed at strategic locations, e.g. at the exit door from a room, down a corridor forming part of the escape route, etc. Those people listening for and following the sound will therefore be led to the most suitable exit from the building to safety.
The noise made by directional sounders is not easily masked by sounds made by the fire alarm (warning tones or bells) and therefore the two can operate simultaneously without issue.
Some directional sounder systems operate in bursts of sound with periods of silence, this allows for voice messages to be broadcast in the gaps between sound bursts. The message may say ‘exit here’ or ‘stairs down here’, or similar to provide additional guidance. The voice messages should not be transmitted at the same time as the bursts of ‘white noise’.
The rate at which the directional sounders give pulses can also be used to provide guidance. The pulse rate of each sounder can be increased, with the one nearest to the exit having the highest pulse rate.
It should be noted that directional sounders are not commonly used in buildings or fire safety designs and are mainly intended for people with sight disabilities. Any design involving their use must ensure compliance with the current standards and codes of practice.
In part 176 of this series, LWF will begin to look at fire safety signs. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact LWF on freephone 0800 410 1130.
Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 35 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.
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.