FIA publishes guidance on BS 5839-1:2025 fire alarm system changes
Iain Hoey
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Major revision to UK fire alarm standard announced
The Fire Industry Association (FIA) has published a new guidance note on BS 5839-1:2025, the British Standard for fire detection and fire alarm systems in non-domestic buildings.
According to the FIA, the document explains key changes introduced in the 2025 edition of the standard, including detector placement rules, system categories, documentation, and cyber security.
The FIA stated that the publication follows its recent national roadshow and online sessions, which were held to support professionals preparing for the updated standard.
The Association said the new guidance provides detailed commentary on the changes affecting system designers, installers, commissioners, and maintainers.
BS 5839-1:2025 replaces the 2017 edition and introduces new content across 26 clauses and annexes.
Updates to system categories and fire detector use
The FIA explained that BS 5839-1:2025 introduces a ban on using heat detectors in rooms where people sleep, including in both Category L2 and L3 systems.
The document adds that sleeping areas are now explicitly defined as high-risk, requiring smoke detection rather than heat-based alternatives.
It also stated that stairway lobbies, previously classed as low-risk, must now be fitted with automatic detection.
Category L4 systems now include recommendations for detectors in flue-like structures, while L3 requirements around ceiling voids have been reworded for clarity.
According to the FIA, detector type and configuration must be recorded and shared during commissioning and maintenance stages.
The guidance note includes new commentary in Annex D on selecting and configuring multi-sensor devices.
Changes to alarm transmission and cyber security
BS 5839-1:2025 sets out updated expectations for fire alarm transmission systems, in light of the UK’s transition to an all-IP network by 2027.
The FIA explained that the standard now includes maximum signal transmission times for Category L and P systems and requires fault reporting within specified timeframes.
A new section has also been added on cyber security and remote access to control and indicating equipment.
According to the guidance note, remote service access should require authentication and risk assessment to prevent unauthorised interference with system performance.
The FIA recommends physical protections such as locking cabinets and tamper-resistant fittings to secure network connections.
It added that a label should be placed at the control panel to remind premises management of ARC connectivity and testing responsibilities.
Documentation and maintenance updates
The 2025 revision includes new clauses on documentation, handover, and record-keeping requirements for fire alarm systems.
The FIA said users must now be given a cause-and-effect matrix or equivalent text description explaining how the system operates.
Maintenance intervals have also been clarified, with a one-month tolerance either side of the six-month servicing cycle now considered acceptable.
The Association explained that fire detection systems linked to alarm receiving centres must have each alarm type tested during servicing to confirm signal transmission.
Routine maintenance must also include functional checks of remote indicators and visual alarms, as well as checks on time clocks and updated system zoning.
Where modifications are made, a new certificate of extension or modification is now required.
Variations, void detection and call point revisions
The guidance note highlights new limits placed on what can be considered acceptable variation from the BS 5839-1:2025 standard.
According to the FIA, certain deviations are now explicitly disallowed, such as omitting a zone plan in multi-zone buildings with sleeping accommodation, or failing to provide ARC signalling in residential care homes.
Further clarification has been added on detector placement around ceiling voids, flue shafts, and structural obstructions.
The FIA said that “closely spaced” ceiling beams are now defined as those less than 1 metre apart centre to centre.
The guidance also confirms new call point rules, including clarified distance and mounting height tolerances.
Where multiple signal types share a sounder, tone differentiation must be used. In schools, class change alerts may now last up to 10 seconds.
Terms, definitions and annex reordering
BS 5839-1:2025 adopts definitions from the newly published BS 4422:2024 Fire Vocabulary.
The FIA stated that this aligns terminology across UK fire safety standards to ensure consistency in interpretation.
New terms have been introduced, including “access room,” “place of ultimate safety,” and “visual display unit.”
Annexes have also been reordered and updated. For example, a new Annex F introduces the formula for calculating false alarm rates and outlines thresholds for triggering investigations.
Annex D has been expanded with more guidance on multi-sensor use.
The guidance confirms that all variations must now be recorded in the system logbook, and firmware updates must be certified as modifications.
FIA publishes guidance on BS 5839-1:2025 fire alarm system changes: Summary
The Fire Industry Association has released a guidance note explaining updates to BS 5839-1:2025.
The standard applies to fire detection and fire alarm systems in UK non-domestic buildings.
The 2025 edition replaces the 2017 version and includes major revisions.
Heat detectors are no longer allowed in rooms where people sleep.
Automatic detection is now required in stairway lobbies.
New recommendations have been added for detector placement in ceiling voids.
The standard introduces transmission time requirements for fire alarm signals.
Cyber security requirements for remote access have been added.
Maintenance tolerances now allow for a one-month variation around six-month cycles.
Cause-and-effect matrices must be provided during system handover.
Some variations from the standard are now prohibited.
All variations must be recorded in the logbook.
Call point distance and mounting height rules have been clarified.
BS 4422:2024 terms are now used throughout the standard.
Annexes have been reordered and expanded to support the changes.