Key Takeaways
In this article
BS 5839-1:2025 was published on 30 April 2025 and replaces BS 5839-1:2017 as the current British Standard code of practice for fire detection and fire alarm systems in non-domestic premises.
For building owners, facilities managers and responsible persons, the publication of a new standard naturally raises questions. Does an existing fire alarm system now need to be upgraded? Are current systems suddenly non-compliant? What has actually changed?
The answer is practical rather than dramatic.
BS 5839-1:2025 does not automatically make every existing fire alarm system non-compliant. Existing systems designed, installed and maintained to the 2017 edition may remain suitable where the building use, fire risk, evacuation strategy and system layout have not materially changed.
However, the 2025 edition does introduce important updates that will affect new designs, extensions, modifications, maintenance, documentation and future compliance reviews. Some changes are clarifications. Others are more significant in practice, especially around manual call points, sleeping accommodation, variations, alarm transmission, system modifications and maintenance records.
This article explains the key changes in practical terms.
BS 5839-1 is the main UK code of practice for the design, installation, commissioning and maintenance of fire detection and fire alarm systems in non-domestic premises.
It applies to a wide range of commercial and public buildings, including offices, factories, schools, hotels, warehouses, shops, healthcare premises, leisure buildings and mixed-use sites.
The standard does not decide whether a fire alarm system is required in a particular building. That normally comes from fire safety legislation, Building Regulations, fire risk assessment, insurer requirements, client requirements or the wider fire strategy.
Once the need for a system has been established, BS 5839-1 gives recommendations for how the system should be designed, installed, commissioned, maintained and documented.
In most cases, no.
The fact that BS 5839-1:2025 supersedes the 2017 edition does not mean all existing systems must immediately be replaced or upgraded. British Standards are codes of practice. They set out recommendations and good practice, but they do not normally operate as retrospective legislation.
The more important question is whether the existing system remains suitable for the current building and fire risk.
If the building has not changed, the system has been maintained properly, documentation is complete and there are no known performance issues, an existing system may remain acceptable.
However, a review becomes much more important where the building has been extended, refurbished, repartitioned, changed occupancy, developed repeated false alarms, added sleeping accommodation or had undocumented fire alarm alterations over time.
For new work, significant upgrades and system extensions, BS 5839-1:2025 should now be the normal reference point.
For projects that were already designed, specified or underway before the 2025 edition was introduced, the position should be reviewed contractually and technically rather than assumed.
In many cases, it may be reasonable for an existing project to continue to the agreed 2017 design basis, particularly where the design has already been approved, procurement has started or installation work is in progress. Where this happens, the project documentation and certificates should make clear which edition of the standard has been used.
For new projects starting after publication of BS 5839-1:2025, the current edition should normally be considered from the outset.
This distinction is important because it avoids unnecessary confusion on live projects while still ensuring new designs are aligned with current good practice.
One of the most useful changes in BS 5839-1:2025 is the introduction of a dedicated section for extensions and modifications.
This is important because many fire alarm problems do not come from the original installation. They come from what happens later.
Buildings change. Offices are divided. Tenants move in and out. New walls are built. Warehouses expand. Production layouts change. Fire alarm systems are then extended, reprogrammed or modified over time, sometimes by different contractors.
The 2025 edition addresses this through the new Section 7, covering extensions and modifications.
The practical message is simple: fire alarm changes should not be treated as casual add-ons.
Where an existing system is extended, the new work should normally be designed and certificated against the current recommendations, while also considering its effect on the existing system. The standard also recognises that if an extension is significant, it may be more appropriate to consider a wider system upgrade or replacement rather than simply adding to an old system.
Clause 45.3 also makes clear that an extended system should be recommissioned to the extent necessary for the new work. This includes considering foreseeable impacts on the existing system, such as battery capacity, radio signal strength and cause-and-effect operation. Clause 45.4 then expects an extensions or modifications certificate to be issued on completion.
For facilities managers, this is a major practical point. If your building is altered, the fire alarm system should be reviewed, tested and documented properly. Adding devices without checking the wider system is not good practice.
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Manual call points are one of the clearest practical changes in the 2025 edition.
Clause 19.2 states that all manual call points should be fitted with a transparent protective cover, which is moved to gain access to operate the device.
This is stronger than simply saying covers may be considered in high-risk locations. The wording means protective covers are now the normal recommended arrangement for manual call points under BS 5839-1:2025.
The intention is to reduce accidental operation, malicious activation and unwanted fire alarm signals. False alarms remain a major issue in many buildings, and manual call points are a common source of unwanted activations, particularly in schools, public buildings, leisure facilities, retail environments and high-traffic areas.
This does not necessarily mean every existing uncovered manual call point in every building must be immediately retrofitted. The standard uses the word “should”, which expresses a recommendation rather than an absolute legal instruction. However, for new systems, significant modifications, extensions and future upgrades, transparent protective covers should now be treated as expected current good practice unless there is a clear and justified reason not to use them.
For existing systems, uncovered call points should be considered during routine maintenance, false alarm reviews and system upgrades. If a building has a history of accidental or malicious activation, retrofitting protective covers is now much easier to justify.
The 2025 edition also simplifies and clarifies manual call point siting.
Manual call points should be located on escape routes and at storey exits and exits to open air that lead to a place of ultimate safety. They should be positioned so that people can raise the alarm quickly as they leave the area or building.
Clause 19.5 states that no one should need to travel more than 45 m to reach the nearest manual call point, measured along the route that a person would actually follow, taking account of walls, partitions and fittings.
Where the final layout is not known at design stage, the straight-line distance from any point to the nearest manual call point should not exceed 30 m. After final fit-out, the 45 m travel distance still applies.
Clause 19.8 gives the mounting height. Manual call points should be fixed at 1.4 m above finished floor level, measured to the centre point of the operating face, with a tolerance of +200 mm and -300 mm. In practical terms, that means the centre of the operating face can be approximately 1.1 m to 1.6 m above finished floor level.
This tolerance is useful because real buildings are not always perfect. Stairs, ramps, glazed partitions, heritage features, accessibility considerations and building finishes can all affect practical mounting positions.
Clause 19.8 also expects manual call points to be easily accessible, well illuminated, conspicuous, free from obstruction and sited against a contrasting background. Where call points are viewed from the side, such as in corridors, Clause 19.9 recommends that they are surface-mounted or semi-recessed so that the front face stands proud by at least 15 mm. Flush mounting can still be suitable where the call point will be readily seen.
There is also an important point for buildings with phased evacuation.
In multi-storey buildings where only certain floors or areas are evacuated at one time, manual call points should be located within the accommodation rather than on stairway landings.
The reason is practical. If a person travelling down a stairway operates a manual call point several floors below the actual fire, it could result in evacuation of the wrong areas.
For phased evacuation buildings, call point location needs to support the evacuation strategy, not undermine it.
Another major practical change relates to rooms in which people sleep.
The 2025 edition places greater emphasis on earlier detection in sleeping-risk accommodation. Clause 7.10 states that, in a Category L1 system, where automatic detection is needed to protect occupants of a room in the event of a fire in that room (for example, where occupants may be asleep), smoke detectors, combustion gas fire detectors or multi-sensor detectors should be provided.
This reflects the wider direction of the 2025 edition, which gives preference to forms of automatic fire detection other than heat detection in rooms where people sleep.
This matters because heat detectors generally respond later than smoke or multi-sensor detectors. In sleeping accommodation, earlier warning is especially important because occupants may not respond quickly to early signs of fire.
Historically, heat detectors were sometimes used in bedrooms or sleeping areas to reduce unwanted alarms. The 2025 edition moves the emphasis towards earlier warning, using smoke, combustion gas or multi-sensor detection where detection is needed to protect sleeping occupants.
This is particularly relevant for hotels, care homes, supported accommodation, student accommodation, staff sleeping areas and mixed-use buildings with sleeping risk.
Existing systems are not automatically condemned, but any future refurbishment, upgrade or review of sleeping-risk premises should consider whether detector selection still reflects current good practice.
The definition of Category L2 has also been revised.
The 2025 standard describes Category L2 as having the same objective as Category L3, with the additional objective of providing early warning to occupants of rooms in which people sleep, and in specified areas of high fire hazard level and/or high fire risk.
This is useful because L2 systems are often misunderstood.
A Category L2 system is not simply “a bit more than L3” or “detection in some extra rooms”. The additional areas should be defined by risk. The specification should identify the rooms or areas that are to be protected and the reason for that protection.
For building owners and consultants, the practical takeaway is that a Category L2 description needs to be clear. If the system is L2, the design information should identify the additional areas covered beyond the L3 baseline, especially sleeping rooms, high fire hazard areas or higher fire risk areas.
Variations are one of the most important changes in BS 5839-1:2025.
A variation is a departure from the recommendations of the standard. Variations are not automatically wrong. In some buildings, they may be necessary because of building constraints, heritage issues, fire engineering solutions, cost-benefit considerations, false alarm risk or practical installation limitations.
However, the 2025 edition makes clear that variations must be handled properly.
Clause 6.1 says variations included within a specification or design proposal should be clearly identified so they are obvious to any party being asked to approve the design. Clause 6.2 says variations identified during installation or commissioning should be documented, with justification, for subsequent approval. Clause 6.3 says all variations should be agreed among the interested parties. Clause 6.4 says all variations should be listed in the relevant system certificate. Clause 6.5 says all variations should be clearly recorded in the logbook so they are available for maintenance companies and other interested parties.
In practical terms, if a variation exists, the responsible person should be able to answer five questions:
This is a major improvement because many old systems contain inherited variations that nobody can properly explain. The 2025 edition pushes the industry towards better accountability.
The 2025 edition also goes further than simply saying variations need to be recorded.
Clause 6.6 identifies departures that are likely to be so detrimental to life safety that they should not be treated as acceptable variations.
These include the absence of a zone plan, or suitable diagrammatic representation, where one is recommended in premises with more than one zone on any storey, particularly where people sleep. They also include the absence of fire alarm transmission to an alarm receiving centre in certain supported housing circumstances where that facility is necessary, and in residential care homes.
The practical point is that not every departure can be justified simply by writing it down.
For example, if a building needs a zone plan to help staff or firefighters identify the location of a fire, the absence of that zone plan should not be treated as an acceptable variation. Similarly, in residential care homes, automatic transmission to an ARC is treated as too important to life safety to be casually omitted.
For responsible persons, this means historic variations should be reviewed. If the variation affects zone information, sleeping risk, care premises or alarm transmission, it should be looked at very carefully.
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BS 5839-1:2025 also gives more specific expectations for automatic transmission of alarm signals to an alarm receiving centre.
Clause 14.17 states that for Category L systems, a fire alarm signal should be received at the ARC within a maximum of 90 seconds. It also states that catastrophic failure of the transmission system, where no alarm signals can be transmitted, should be indicated at both the ARC and the control and indicating equipment within 3 minutes.
Clause 14.18 gives a different timing for Category P systems. In that case, the alarm signal should be received at the ARC within a maximum of 120 seconds, with catastrophic failure also indicated at the ARC and CIE within 3 minutes.
This distinction matters because Category L systems are concerned with life safety, while Category P systems are concerned with property protection.
Clause 14.22 also requires a label on or adjacent to the CIE where automatic transmission to an ARC is provided. The purpose is to help avoid false activation that could summon the fire and rescue service.
For building owners, this means monitored fire alarm systems should be reviewed not just for whether they send a signal, but whether they send the right signal, within the expected time, with the correct information and suitable warning at the panel.
Another practical change is the way sound pressure levels are measured.
Clause 15.1.1 now makes clear that alarm sound pressure levels should be measured with all doors shut.
That sounds like a small change, but it can matter in real buildings. Doors, partitions and acoustic treatments can significantly reduce sound levels. Measuring with doors shut better reflects the actual conditions under which occupants may need to hear the alarm.
For most Category M and Category L systems, the familiar benchmark remains 65 dB(A) throughout accessible areas, with exceptions such as 60 dB(A) in stairways, cellular offices and certain limited areas. Where the system is intended to rouse people from sleep, the sound pressure level should be at least 75 dB(A) at the bedhead.
The practical point is that buildings that have been repartitioned, fitted with acoustic doors or changed layout may need sound levels rechecked. A system that was adequate when originally installed may not provide the same audibility after building changes.
The 2025 edition recognises that fire alarm systems are sometimes discussed in relation to lockdown arrangements, particularly in schools.
Clause 15.1.12 states that fire alarm evacuation tones should not be used for purposes other than warning of fire, except where the required response is identical to fire evacuation, or in schools where the fire alarm signal is used for the start or finish of predetermined periods, with class-change signals not exceeding 10 seconds.
The standard includes a note pointing to FIA guidance on the use of fire alarm systems for lockdown in schools.
The practical message is that fire alarm tones should not be casually reused for other alerts. If lockdown or non-fire warnings are needed, they should be carefully designed so they do not cause confusion with the fire evacuation signal.
The 2025 edition gives clearer attention to the impact of obstructions close to ceilings.
Clause 21.2.12 deals with obstructions that are close to the ceiling and explains when they should effectively be treated as walls for detector siting purposes. This includes situations where an obstruction has a gap of less than 300 mm from the ceiling and where the obstruction height is greater than 10% of the room height.
This is relevant because many buildings change internally after fire detection is installed. Storage racks, partitions, plant, ductwork, shelving and other obstructions can all affect how smoke or heat reaches detectors.
The practical message is simple: detector layouts should be reviewed when the room layout changes. A detector that was correctly sited before a fit-out may become compromised if new partitions, racking, ductwork or ceiling-level obstructions are introduced.
For responsible persons and facilities managers, this means that fire alarm compliance should not only be checked when the system is first installed. It should also be reviewed after refurbishments, storage changes, racking installations, plant changes or internal layout alterations.
The 2025 edition gives clearer attention to the role of flue-like structures in escape route protection.
For Category L4 systems, Clause 21.1.3 now states that a fire detector should be sited at the top of a shaft or flue-like structure, such as a lift shaft, escalator shaft, hoist shaft or enclosed chute, where it penetrates one or more ceilings.
This is a useful reminder that smoke movement is not limited to corridors and stairways. Vertical shafts and similar structures can create routes for smoke travel, and the fire detection strategy should take this into account.
For responsible persons, this is most relevant during design reviews, refurbishments, lift works or assessments of older L4 systems.
BS 5839-1:2025 continues to place strong emphasis on routine inspection, testing and servicing.
Clause 43.2.1 states that successive inspection and servicing visits should be undertaken at intervals of approximately six months. It also notes that it is acceptable for one inspection, test and service to be carried out between 5 and 7 months after the previous visit.
That is useful practical clarification. It recognises real-world scheduling while still maintaining the general six-monthly service expectation.
The standard also expects the logbook to be examined, outstanding faults to be reviewed, structural or occupancy changes to be checked, false alarm records to be reviewed, batteries to be tested and system functions to be checked.
Importantly, Clause 43.2.3 expects visual inspection to consider whether building changes have affected manual call points, automatic detectors and fire alarm devices. This includes checking that manual call points remain unobstructed and conspicuous, that new exits to a place of ultimate safety have adjacent call points, that partitions and storage have not compromised detectors, and that changes in use have not made detector types unsuitable or prone to unwanted alarms.
This is an important message for building owners: servicing is not just pressing a button and issuing a certificate. It should include a practical review of whether the system still suits the building.
The 2025 edition also includes useful maintenance clarifications.
Clause 43.2.10 now requires the timeclock to be checked and adjusted if it is not showing the correct time. This matters because event logs, time-related detection settings and alarm histories all depend on accurate system time.
Clause 43.3.5 states that a functional test should be carried out on every detector to determine whether products of combustion, such as smoke, heat or gas, can pass unhindered between the protected area and the sensing chamber or elements.
This is particularly relevant where detectors include self-testing features. A detector may be able to test its electronics, but the system still needs confidence that smoke, heat or gas can actually reach the sensing element from the protected space.
The method of confirming this is not fixed in the standard. It is for the manufacturer and/or maintenance company to determine the appropriate method.
The model logbook in Annex H has been updated. The contents page shows new model logbook sections for cause-and-effect programming and agreed variations.
This is a practical and important change.
Cause-and-effect information is vital for systems that interface with plant, lifts, smoke control, suppression, doors, shutdowns, staged alarms or alarm transmission. Agreed variations are equally important because future engineers, maintainers and responsible persons need to understand why the system differs from normal recommendations.
A fire alarm logbook should not be treated as a paperwork extra. It is part of the system’s compliance history.
The sensible response to BS 5839-1:2025 is review, not panic.
Building owners and responsible persons should check whether the current system documentation is complete, whether previous variations are recorded, whether the logbook is being maintained properly and whether any building changes have affected the system.
Particular attention should be given to manual call point covers, manual call point locations, sleeping-risk accommodation, alarm transmission to ARCs, false alarm history, sound levels, zone plans, cause-and-effect programming and any extensions or modifications carried out over the years.
If the system is being extended or modified, the new work should be designed, recommissioned and certificated properly in line with the 2025 edition.
Where there is any doubt, the best starting point is a competent fire alarm review rather than assuming the existing system is either fully compliant or completely obsolete.
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BS 5839-1:2025 is not a complete reinvention of fire alarm design, but it is an important and practical update.
The strongest themes are clearer accountability, better documentation, better control of variations, improved false alarm reduction, clearer manual call point recommendations, stronger consideration of sleeping risk and better management of extensions and modifications.
For many buildings, the key issue will not be whether the original system once complied with BS 5839-1:2017. The more important question is whether the system still reflects the current building, current occupancy and current fire strategy.
Astro Fire Systems can support BS 5839 compliance reviews, fire alarm upgrades, system extensions and modifications, detector suitability reviews, false alarm investigations, maintenance, servicing and fire detection design for commercial, industrial and specialist environments.
A fire alarm system is not a fit-and-forget installation. Buildings change, risks change and standards evolve. BS 5839-1:2025 gives building owners and responsible persons a clearer framework for keeping fire detection and alarm systems effective, documented and suitable for the risks they are designed to protect.
BS 5839-1:2025 - fire detection and fire alarm systems for buildings, code of practice for non-domestic premises
BS 5839-1:2017 - superseded edition, which may remain the design basis for existing systems and projects already underway
BS EN 54 series - components for fire detection and fire alarm systems
BS 8591 - remote centres receiving signals from alarm systems
FIA guidance on the use of fire alarm systems for lockdown in schools
Regulatory Reform (Fire Safety) Order 2005 - duties of the responsible person
Building Regulations Approved Document B - fire safety
Insurer requirements
Site-specific fire risk assessment and fire strategy
In most cases, no. The publication of BS 5839-1:2025 does not automatically make existing fire alarm systems non-compliant or require them to be replaced. A fire alarm system designed and installed in accordance with a previous edition of the standard may remain acceptable provided it continues to be suitable for the building, is properly maintained and the fire risk assessment does not identify any significant deficiencies.
The suitability of an existing system should be considered in conjunction with the fire risk assessment, the building's use, occupancy profile and any changes that may have occurred since the system was originally installed. Alterations to the building, changes in occupancy, changes in fire risk or significant modifications to the fire alarm system may all trigger a review of whether the existing design remains appropriate.
BS 5839-1:2025 is primarily intended to influence new installations, system extensions, major modifications and future fire alarm design decisions. In these circumstances, the current edition of the standard would normally be used as the design benchmark.
The key question is not simply when the system was installed, but whether it remains suitable for the risks it is intended to protect. A well-maintained system designed to a previous edition of the standard can often remain acceptable for many years, provided it continues to satisfy the needs of the building and its occupants.
Reviewed by David Cullis, Managing Director, Astro Fire Systems Ltd. BAFE accredited (SP203-1 and SP203-3).
BS 5839-1:2025 recommends that manual call points should be fitted with transparent protective covers, but the publication of the new standard does not automatically mean that every existing call point without a cover must be replaced or upgraded.
The recommendation has been introduced primarily to help reduce unwanted fire alarm activations caused by accidental operation, misuse or malicious activation of manual call points. Protective covers provide an additional level of protection whilst still allowing rapid operation in the event of a genuine fire emergency.
For new fire alarm installations, significant system modifications and extensions designed to BS 5839-1:2025, transparent covers would normally be expected unless there is a justified reason for adopting an alternative approach. For existing systems installed to previous editions of the standard, the absence of covers does not automatically render the system non-compliant.
As part of routine maintenance reviews, fire risk assessments or future upgrade works, building owners may wish to consider whether protective covers would provide a practical benefit, particularly in locations where unwanted alarms have historically been an issue. Schools, public buildings, healthcare environments and other high-occupancy premises may particularly benefit from their use.
As with many recommendations contained within BS 5839-1, the objective is to improve the overall performance and reliability of the fire alarm system rather than to create an immediate requirement for wholesale replacement of existing equipment.
One of the notable changes within BS 5839-1:2025 relates to the approach taken towards fire detection in sleeping accommodation. The updated guidance places greater emphasis on the use of detector types capable of providing earlier warning of fire where people may be asleep and less able to respond quickly to developing fire conditions.
The standard now generally favours smoke detectors, combustion gas detectors or appropriately selected multi-sensor detectors in many sleeping risk environments. The intention is to improve the likelihood of detecting a developing fire at an earlier stage compared with relying solely on heat detection.
This change reflects the reality that heat detectors typically respond later in the development of a fire. In premises where occupants may be asleep, early warning can be critical in providing sufficient time for evacuation and emergency response.
Hotels, guest accommodation, care homes, student accommodation and other buildings containing sleeping risks may therefore see different detector selection decisions under BS 5839-1:2025 compared with some historical designs.
However, the publication of the new standard does not automatically make existing systems non-compliant. Where heat detectors already exist within sleeping accommodation, their continued suitability should be considered as part of the fire risk assessment, maintenance reviews and any future refurbishment, extension or upgrade works.
The objective of the revised guidance is to encourage earlier fire detection and improved life safety outcomes rather than to require immediate replacement of existing systems that were designed in accordance with previous editions of the standard.
BS 5839-1:2025 continues to recognise that variations from the recommendations of the standard may sometimes be necessary. However, the updated edition also identifies certain departures that should not be regarded as acceptable variations because of their potential impact on life safety.
A variation is intended to document and justify a departure from the recommendations of the standard where an alternative approach has been adopted. Historically, provided the variation was properly recorded and agreed, many departures could be managed in this way. The 2025 edition places greater emphasis on ensuring that variations do not undermine the fundamental objectives of the fire alarm system.
Clause 6.6 now includes examples of situations that should not simply be accepted as variations. These include certain omissions relating to life-safety provisions where the absence of the recommended measure could significantly affect the effectiveness of the fire alarm system or the safety of occupants.
For example, the standard identifies the absence of a zone plan in certain premises containing sleeping accommodation and the absence of automatic alarm transmission in certain care and supported housing environments as examples of departures that should not merely be documented and accepted as variations.
The key principle is that a variation should not be used to justify the omission of a measure that is fundamental to the safe operation of the fire alarm system. Where a departure creates an unacceptable reduction in life safety, the appropriate solution is normally to rectify the deficiency rather than record it as a variation.
Building owners, Responsible Persons and fire alarm professionals should therefore ensure that all proposed variations are carefully assessed, properly documented and reviewed in the context of the fire risk assessment and the overall objectives of the fire alarm system.
Any variation from the recommendations of BS 5839-1 should be clearly documented and recorded so that future owners, maintainers, fire risk assessors and enforcing authorities can understand what departure has been made and why.
Variations should not only be recorded within the fire alarm logbook, but should also be referenced within the relevant design, commissioning and certification documentation where appropriate. The record should clearly identify the nature of the variation, the reason for the departure, any compensatory measures that have been implemented and the parties responsible for agreeing the approach.
BS 5839-1:2025 places increased emphasis on ensuring that system documentation provides a clear record of variations and system operation. The updated model logbook contained within Annex H includes dedicated sections for recording variations and documenting cause-and-effect arrangements to help improve transparency and traceability throughout the life of the system.
Variations should also be reviewed periodically, particularly where there have been changes to the building, occupancy, fire risk assessment or fire alarm system. A variation that was considered reasonable when originally agreed may no longer remain appropriate if the circumstances of the building change.
Good variation records should allow a competent person reviewing the system many years later to understand exactly what differs from the recommendations of the standard, why that decision was made and whether the justification remains valid.
The objective is not simply to create paperwork, but to ensure that all stakeholders have a clear understanding of how the fire alarm system has been designed, installed and maintained throughout its operational life.
Whether you need an existing fire alarm system reviewed, an extension or modification designed and certificated, or ongoing maintenance support, our engineers can help. Call 01905 964703 or request a free site survey.
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