The LWF Blog
Fire Safety for Facilities Management Personnel – Fire Detection & Fire Alarms – Part 193
March 20, 2023 12:18 pmLawrence 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 192, LWF looked at the control and indicating equipment of a fire alarm installation. In part 193, we consider alarm devices.
The most common sound for a fire alarm is either a bell or an electronic sounder, although they are not the only fire alarm sounder options available. The choice of sounder is largely a matter of individual choice when installing a fire alarm system, although other factors may have a bearing on the most suitable choice for a given environment. Whatever choice is made, the sounder should be consistent throughout a building. It would be potentially confusing to have two different forms of sounder as a means of giving warning about fire.
The sound level of the fire alarm in an otherwise quiet building should be not less than 65 dB(A) in most areas, or in a building with background noise, the alarm should be at least 5 dB(A) above other noises. Within stairwells and small rooms, the sound level may be reduced to around 60 dB(A) and this level is also acceptable at the most remote point from the fire alarm sounder, if the level of 65 dB(A) is achieved in the majority of the area.
The above levels are given on the basis of an environment where all building occupants are awake and alert. When people may be sleeping, such as in a hotel, it is important that the alarm sounder is loud enough to rouse them from sleep. For this reason, the sound level at a bedhead in a hotel should be 75 dB(A), as with any other sleeping environments, except hospitals where the alarm is not always intended to wake patients but to alert staff and other occupants of the need to evacuate.
In patient-care areas of healthcare buildings, the recommended level by the Department of Health guidance recommends a sound pressure level between 40 dB(A) and 55 dB(A). The lower of the two pressure levels ensures that staff will hear and act upon the alarm and the maximum level of 55 db(A) is intended to ensure the alarm is not disruptive for ill patients.
In part 194 of this series, LWF will continue discussing the sound pressure levels of alarm sounders. 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.