Warehouses are the lifeblood of many industries, holding the inventory and materials that keep businesses running. But with great capacity comes great risk. Ensuring your warehouse is equipped with a reliable fire detection system is not just a legal responsibility - it is a commitment to safeguarding your team, your assets and your operations.
Industrial premises, including warehouses, accounted for 1,656 fires in England in 2024/25, according to the MHCLG fire statistics data tables (table FIRE0304). And the financial stakes are severe: a major fire can destroy stock, halt trading for months and leave a business unable to reopen at all.
This guide walks you through the essential considerations for warehouse fire detection - from compliance and technology to the specific challenges of large-space detection that the industry rarely discusses clearly.
In the UK, the Regulatory Reform (Fire Safety) Order 2005 (FSO) is the primary fire safety legislation for commercial premises in England and Wales. It places duties on the Responsible Person - typically the employer, building owner or facilities manager - rather than prescribing specific technical solutions.
Under Article 13 of the FSO, the Responsible Person must ensure premises are equipped with appropriate fire detectors and alarms "where necessary" and "to the extent that it is appropriate" - taking into account the size, use and occupancy of the premises. Under Article 17, fire safety equipment must be maintained in efficient working order.
Critically, the FSO does not specify system categories, detector types or testing frequencies. That technical detail is provided by BS 5839-1:2025 - the current edition of the British Standard code of practice for fire detection and alarm systems in non-domestic premises, published on 30 April 2025. BS 5839-1 is not legislation, but it represents the accepted benchmark of good practice, and fire authorities and courts treat it as such.
For warehouses, compliance means starting with a suitable and sufficient fire risk assessment, appointing a competent Responsible Person and implementing a detection strategy matched to your specific premises. Regular audits, staff training and meticulous record-keeping are all part of the picture.
There is no shortcut past the risk assessment. BAFE's guidance for its SP203-1 scheme stresses that third-party certification exists to provide independent evidence of a provider's competence to design, install, commission and maintain fire detection and alarm systems - and that Responsible Persons should verify a provider's certification before awarding any contract. Every decision about system category, detector type and maintenance frequency flows from the risk assessment, not from assumptions about what a "standard" warehouse needs.
BS 5839-1:2025 defines eight system categories across three types. The right category for your warehouse is determined by fire risk assessment - not by building type alone. Here is what the categories mean in practice:
Mixed categories are common and entirely acceptable under BS 5839-1:2025. A warehouse might operate an L2/P1 system, for example, combining life-protection coverage of hazardous zones with full property-protection detection across the building.
The Fire Industry Association (FIA) notes that for most warehouses, automatic detection will typically be at Category L2 or P1 level - but the fire risk assessment is the only legitimate basis for that decision.
Warehouses are unique environments. The right detection technology depends on ceiling height, storage configuration, goods stored and environmental conditions such as dust and airflow.
In a standard office or retail space, smoke from a fire rises to the ceiling and reaches a detector within seconds. In a high-bay warehouse, this does not always happen.
As hot smoke rises through a large, cold air mass, it cools and loses buoyancy. It can form a stable horizontal layer - a stratification layer - well below the ceiling and, crucially, well below ceiling-mounted detectors. Research published by the Fire Industry Association confirms that predicting exactly where stratification will form is extremely difficult, because it depends on the energy of the fire, the temperature gradient in the space, ambient weather conditions and the time of day. A fire can smoulder and grow undetected for a significant period while smoke sits beneath the detection layer.
This is not a theoretical risk. It is a practical engineering challenge that demands the right detector technology and placement strategy from the outset.
Optical beam detectors are the most widely specified primary detection technology for high-bay warehouses. A transmitter projects an infrared beam across the space; a receiver on the opposite wall monitors the received light. When smoke crosses the beam and reduces light transmission beyond a preset threshold, an alarm is raised.
Strengths:
Limitations:
Addressing stratification with beam detectors: BS 5839-1:2025 recommends that where stratification risk is significant, supplemental detection at intermediate heights should be considered. FIA research confirms that beams installed horizontally at an intermediate height - passing through a potential stratification layer - are effective at detecting fires that would otherwise not be detected by ceiling-mounted devices.
Blake's designs beam detection layouts for warehouses across Essex and London, taking into account building height, structural beams, racking layout and airflow patterns to minimise coverage gaps from the outset.
Aspirating smoke detection - also known as air-sampling detection or by the VESDA brand name - actively draws air through a network of sampling pipes to a central, highly sensitive laser-based detection unit. Rather than waiting for smoke to drift to a detector, the system goes to the smoke.
Strengths:
Limitations:
ASD is governed by BS EN 54-20 and is classified into sensitivity classes (A, B and C). For warehouse applications, the appropriate class depends on the fire risk assessment - there is no single default. BS 5839-1:2025 recommends multi-level sampling for high-bay spaces unless the risk of stratification is minimal.
Standard optical (photoelectric) point detectors are appropriate for lower-ceiling warehouse areas - typically up to approximately 10.5 metres. They are the most economical option and are suitable for ancillary areas such as offices, break rooms and loading bays with normal ceiling heights. BS 5839-1:2025 requires that detectors are not sited closer to structural beams or ductwork than twice the depth of the obstruction, to avoid smoke flow being disrupted.
Heat detectors - which sense temperature, not smoke - are appropriate where smoke detectors would generate excessive false alarms: battery-charging areas, dusty manufacturing spaces and some loading dock environments. They are slower to respond than smoke detection and should not be used as a substitute for smoke detection where smoke detection is practicable. Heat detectors detect heat only; they will never detect smoke under any conditions.
High-bay racking creates its own detection challenges. Rack systems can obstruct smoke flow to ceiling-mounted detectors, creating dead zones within aisles. Some risk assessments identify the need for in-rack detection - detectors mounted at rack level to catch fires that originate within pallet loads before smoke can rise.
Martin Blake, Blake's Passive Fire Safety Manager, calls this the mistake he sees most often on site:
"The biggest one is changes to racking without thinking about whether the fire alarm needs changing. If racking is installed with the top shelf two metres from the ceiling, the fire alarm will have been designed as though nothing is there. If the shelving is then changed and stock ends up within 500mm of the ceiling, that has to be treated like a wall and additional devices might be needed. Another common one is forklifts hitting beam detectors and causing false alarms."
Martin Blake, Passive Fire Safety Manager, Blake Fire & Security Systems (LinkedIn)
Mezzanine floors introduced after original installation are a particularly common coverage gap. Detection designed for the original ceiling level provides no coverage for fires that start on or below the mezzanine. Any structural modification to your warehouse should trigger a review of your fire detection design.
BS 5839-1:2025 is clear that void spaces over 800mm deep require detection coverage in Category L1 systems. For Category P1 systems (full property protection), voids also require coverage.
The risk is not hypothetical. Two significant incidents in the past year illustrate how rapidly warehouse fires escalate and how important early detection is.
In November 2025, a warehouse fire on Bridge Road, Southall, required 25 fire engines and approximately 150 firefighters from London Fire Brigade. A major incident was declared. Explosions from cylinders and fireworks stored in the building caused the roof to collapse and destroyed the structure entirely. Around 1,000 local residents were evacuated. (London Fire Brigade, November 2025)
In July 2026, a warehouse fire on Watermead Way, Tottenham, required 15 fire engines and around 100 firefighters. Approximately 20 vehicles were destroyed and an adjoining building was partially damaged. The Brigade's drone team was deployed to support the Incident Commander. The cause remains under investigation. (London Fire Brigade, July 2026)
In both cases, the scale of the response - and the destruction - is a reminder of what adequate early detection is designed to prevent.
Warehouse design and fire detection are inseparable. The features of your building directly influence how smoke and heat behave in a fire.
Ventilation systems that help keep the building comfortable during operations can actively hinder detection if not designed in coordination with the fire alarm system. Airflow from loading bay doors or HVAC units can disperse smoke before it reaches a detector or carry it away from sampling pipes.
Racking layouts should be reviewed as part of any detection design. Proper aisle spacing and strategic detector placement can mitigate the blind-spot risk that dense racking creates. Blake's engineers assess these factors as part of every warehouse detection survey - working to the spatial coverage requirements of BS 5839-1:2025 and the specific detection technologies being deployed.
Even the most sophisticated detection system can fail if maintenance is neglected. BS 5839-1:2025 sets out the following recommendations - note these are recommendations of the standard, not legal requirements in themselves (the FSO requires a suitable system of maintenance, but does not specify frequencies):
For ASD systems, the pipe network and sampling holes also require periodic inspection - blocked holes reduce the volume of air sampled and degrade system sensitivity.
Neglecting maintenance does not just risk system failure - it creates legal exposure under Article 17 of the FSO, can invalidate insurance and means maintenance records are unavailable if a claim is made.
Blake's NSI Gold and BAFE SP203-1 registered maintenance contracts are designed to keep your warehouse fire detection system compliant with BS 5839-1:2025, with documented service certificates after every visit.
Fire detection works best as part of a coordinated system, not in isolation. Common integrations for warehouses include:
Wherever your fire alarm connects to another system, that link should be written down in a cause-and-effect matrix - BS 7273-6:2019 sets out the format - so everyone knows exactly what triggers what. Fire safety functions must always take priority - integration should never compromise the alarm's ability to operate.
The regulatory picture is also shifting. Formal fire safety notices issued in England rose to 2,972 in 2024/25 - up 5.3% on the previous year, according to MHCLG fire prevention statistics. Enforcement is increasing, and the consequences of inadequate fire safety arrangements are real: fire safety prosecutions rose 79% in 2023/24.
Electrical distribution faults remain the single largest identifiable cause of workplace fires - responsible for approximately 18% of incidents in 2024/25, according to MHCLG fire statistics. For warehouse operators, this points directly to the importance of regular electrical testing and ensuring battery-charging stations are sited in well-ventilated areas with appropriate detection.
Since 1 April 2025, responsibility for fire statistics and policy in England has transferred from the Home Office to the Ministry of Housing, Communities and Local Government (MHCLG).
Investing in a fire detection system is a long-term commitment. The initial cost of a well-designed beam detection or ASD system must be weighed against the potential cost of a fire - lost stock, lost buildings, lost trading time and the very real possibility that a business that cannot recover quickly may not reopen at all.
A cost-effective plan for your warehouse should include:
Not always - at least not in the form of a full automatic fire detection system. The Regulatory Reform (Fire Safety) Order 2005 requires the Responsible Person to ensure fire detectors and alarms are in place "where necessary" and "to the extent appropriate," based on a fire risk assessment. For most warehouses - particularly those with staff present, flammable materials or high-value goods - a proper fire alarm system will be appropriate and necessary. But the legal trigger is the risk assessment, not the building type. Speak to a competent fire risk assessor to determine your specific obligations.
Smoke stratification happens when smoke from a fire cools as it rises and loses buoyancy, forming a stable horizontal layer below the ceiling rather than continuing to rise. In high-bay warehouses, this layer can form well below ceiling-mounted detectors, allowing a fire to grow significantly before any alarm is triggered. It is one of the primary reasons specialist detection technologies - beam detectors at intermediate heights or aspirating systems with sampling points at multiple levels - are recommended over simple ceiling-mounted point detectors in tall warehouse spaces. The Fire Industry Association has published research confirming that stratification height is very difficult to predict, making a conservative, layered detection approach the prudent choice.
Both technologies are designed for large-space detection, but they work differently. Beam detection projects an infrared beam across the space; smoke crossing the beam triggers an alarm. It offers cost-effective coverage of very large open areas but relies on smoke reaching the beam path - making detector positioning critical in high-bay spaces. Aspirating smoke detection (ASD) actively draws air through sampling pipes to a highly sensitive central unit. It can detect smoke at far lower concentrations than a beam detector, provides very early warning and can sample at multiple heights - which directly addresses the stratification risk. ASD is particularly suited to cold-storage facilities, high-value goods warehouses and any space where the earliest possible detection is critical. Your fire risk assessment and a specialist survey should determine which is right for your facility.
BS 5839-1:2025 recommends professional servicing by a competent fire alarm engineer at least every six months (the standard permits a window of five to seven months between visits). Weekly, the Responsible Person should test at least one manual call point on a rotating basis and record the result. Higher-risk or complex warehouses may require quarterly professional servicing - your fire risk assessment should specify the appropriate frequency. It is worth noting that these are recommendations of the standard; the Regulatory Reform (Fire Safety) Order requires a "suitable system of maintenance" but does not set specific intervals.
Standard optical point smoke detectors have practical limitations at height. BS 5839-1:2025 guidance and industry practice generally treat approximately 10.5 metres as the ceiling height above which point detectors alone are typically unsuitable as the primary detection method. Above this height, beam detection or ASD is recommended. Even below this threshold, the risk of smoke stratification in warehouses with significant air movement or temperature differentials means that a specialist survey is advisable before relying solely on ceiling-mounted point detectors.
Fire detection in a warehouse is not a checkbox exercise - it is a genuinely specialised discipline. The combination of high ceilings, complex storage configurations, demanding environmental conditions and the stratification challenge means that the design approach that works in an office or retail space will not necessarily protect your warehouse.
The right solution starts with a proper fire risk assessment, followed by a system design that accounts for the specific characteristics of your building. Whether that means beam detection, aspirating smoke detection, a combination of both or supplemental detection at intermediate heights - the decision should be evidence-based, not assumption-based.
Is your warehouse detection system designed for the building you actually have? Blake's surveys warehouses across Essex and London and designs systems to BS 5839-1:2025. Our team holds NSI Gold and BAFE SP203-1 registration - backing that goes beyond self-certification. Call us on 01702 447800 or visit our fire alarms page to find out what the right system looks like for your operation.
Blake's is a family-run fire and security business, founded in Southend in 1979 and operating from our Essex headquarters. We hold NSI Gold certification, BAFE SP203-1 registration and SSAIB certification - each independently audited, not self-declared. Our fire alarm team designs, installs, commissions and maintains systems for warehouses, commercial premises and schools across Essex, London and the wider South East. We have two NSI Gold-approved registered fire system designers on staff.
"Big enough to cope, small enough to care" - the surveyor who assesses your site will introduce you to the engineer carrying out the work.
Commercial fire alarm systems | Fire alarm maintenance | Fire alarm monitoring
This article is provided for general information and educational purposes only. It is not legal advice, a fire risk assessment, a compliance audit, a technical specification or a substitute for advice based on inspection of your premises. Fire safety and security legislation, standards, guidance and enforcement practice can change. For advice about fire alarm systems for your specific premises, call Blake's on 01702 447800. For legal advice or confirmation of your statutory duties, consult an appropriately qualified legal adviser or competent fire risk assessor.
