The LWF Blog
Fire Safety Engineering for Design – Fire Detection & Alarm Systems – Part 167
January 22, 2024 12:03 pmLWF’s Fire Safety Engineering blog series is written for Architects, building designers and others in the construction industry to highlight and promote discussion on all topics around fire engineering. In part 166, LWF looked at the recommendations and guidance for fire alarm sounders as per BS 5839-1 and NFPA 72. In part 167, we continue talking about the requirements when NFPA 72 is the relevant standard and will look at how fire alarms connect with other fire safety measures.
According to NFPA 72, the maximum sound level of a fire alarm sounder should not exceed 120 dBA for any type of system and no matter the background noise or placement. Mechanical equipment rooms should be designed with a level of 85 dBA.
NFPA 72 also states that temporal audible signals should be used so there is a clear definition of the fire alarm signal across installations.
The use of visual alarms or an alternative should be determined on a local basis, where NFPA 72 is applied. In the US, this is covered by the Americans with Disabilities Act, which provides guidance on the stringent measures required for the type and use of building.
Other Fire Safety Measures
When a fire is detected, a fire alarm system is capable of doing more than simply triggering the fire alarm sounders. They may be used to activate other fire safety measures. Some examples are:
- Disabling lift mechanisms
- Activating fire suppression controls
- Activating public address announcements about the fire
- Automatically closing smoke and fire doors
- Shutting down plant and machinery
- Activating smoke control systems
In some environments, it may be preferable to fit more than one fire alarm panel in a building so that all the cabling for each element does not have to terminate at a single control point. Where more than one alarm panel is used, it may be necessary for the initial fire alarm panel to send signals to the other alarm panels (and from there to activate any other fire safety measure, as designed).
Fire alarm panels are also often used to send signals to building management systems, radio paging systems, communication monitoring systems or off-site monitoring stations.
Fire alarm panels may also work alongside a PC system so that graphical and textual information can be displayed on a screen. Events taking place, such as fire safety measure activations, communications etc. can be stored by the PC in a log and printed out for use. Such information may be useful to the Fire Service when they attend or after the fire is put out for company and insurer information.
In part 168 of LWF’s series on fire engineering we will talk about the cabling used in fire alarm 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 since 1986 to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact the LWF office on 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.