The LWF Blog
Fire Safety Engineering for Design – Fire Detection & Alarm Systems – Part 140
July 10, 2023 12:31 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 139, LWF discussed the different types of property protection as per NFPA 72, before beginning to look at fire detection and fire alarm systems for life protection. In part 140, we look at the categorisation of life safety fire alarm systems as per BS 5839-1.
BS 5839-1 provides guidance on the various categories of life safety fire alarm systems. Category L systems are subdivided as follows:
L1 Fire Detection and Alarm Systems:
Detectors are required in all areas, with a few exceptions. Exceptions may include some voids of loss than 800 mm in height, unless fire spread between rooms could take place, small cupboards less than 1m2, toilets, bathrooms, some small lobbies. Floor voids in data processing rooms are to be protected, irrespective of depth. This is classed as comprehensive coverage and is as per a category P1 system.
L2 Fire Detection and Alarm Systems:
An L2 system is designed so as to protect the escape route and any high risk areas. Detectors will cover the entirety of the escape route and any routes and rooms that open directly onto it. Exceptions are made, as per L1.
The system will cover any high risk areas – the high risk element may pertain to areas where the probability of fire is high, the level of combustibles stored is high or the risk to life is high.
As the escape route part of protection also pertains to an L3 level fire alarm system, the particular L2 relevance pertains to the designer defined areas of high risk.
L3 Fire Detection and Alarm Systems:
As L2 above, the system is designed to protect escape routes and rooms opening onto escape routes including stairways, corridors and any other relevant areas forming part of the escape route. There are exceptions as per L1 and L2.
L4 Fire Detection and Alarm Systems:
To protect escape routes, stairways, corridors and other parts that form the escape route.
L5 Fire Detection and Alarm Systems:
To provide protection in selected rooms and areas only. This type of system is normally provisioned to achieve a specific fire safety goal.
In part 141 of LWF’s series on fire engineering, we will look at the category L fire detection and alarm systems in more detail. 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.