The LWF Blog

Fire Safety Engineering for Design – Fire Detection & Alarm Systems – Part 137

June 19, 2023 10:48 am

LWF’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 136, LWF discussed false fire alarms and what can be done to remedy repeated false alarm signals. In part 137, we begin to look at the classification of fire alarm systems.

There are two main standards offering classification of fire alarm systems recognised in most parts of the world. The first is BSI (British Standards) which is used in the UK and abroad. The second is NFPA (National Fire Protection Association) which is used in the United States and recognised in many other countries.

The two systems offer different approaches. The BSI system classifies systems as being for property or life, with a separate standard relating to dwellings – BS 5839-6.  NFPA 72 designates alarm systems as those designed for households, for protected premises and for those requiring supervising station cover.

Fire Alarm Systems found in Households

NFPA 72 identifies fire alarm systems for household protection as one of three main types. British Standards splits domestic and non-domestic systems into separate standards.

Fire Alarm Systems for Property Protection

British Standards refers to fire alarm systems for property protection purposes as a category P system. Such systems are designed to automatically detect a fire at an early stage, indicate the location at the control and indicating equipment and raise an alarm in time to summon the Fire Service and any in-house firefighting team. A category P system is required to transmit a signal to an alarm receiving centre so that the Fire Service may be notified of the need to attend.

As a category P fire alarm system is not one specifically designed for life safety (which has the designation L category) the requirement to have an auditory alarm may be reduced depending upon the type of building, potential occupation and resulting need for any occupants to evacuate.

The NFPA 72 standard does not differentiate between systems designed to protect property or life, therefore all aspects are covered under the protected premises system type.

BS 5839-1 provides sub-divisions for category P fire alarm systems which will be laid out in the next part of this blog series.

In part 138 of LWF’s series on fire engineering, we will continue to discuss the classifications of fire alarm systems as per BSI and NFPA. 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.