Introduction
Emergency lighting remains one of the most critical yet often overlooked safety systems in our buildings. While it operates quietly in the background, its role during power failures or emergencies is absolutely vital. Guiding people to safety, supporting those who must remain in place, and enabling essential operations to continue. The publication of BS 5266-1:2025 represents a significant evolution in how we approach these life safety systems, and as technical consultants, we've been working through the implications for our clients and the industry.
Beyond Escape Routes: A Fundamental Shift in Scope
The most transformative change in BS 5266-1:2025 is the expansion of scope beyond traditional emergency escape lighting. The standard now formally addresses three distinct categories of emergency lighting, reflecting the complexity of modern building use and evacuation strategies.
Emergency escape lighting continues to provide the illumination needed to guide occupants safely to an exit during an emergency. This remains the core function we're all familiar with.
Local area lighting is now explicitly covered, providing illumination to specific points or tasks where people need to safely complete vital activities during a power failure. This acknowledges that not every emergency requires immediate evacuation.
Standby lighting allows normal activities to continue when the main power supply is lost, supporting business continuity and operational resilience.
This broader perspective is a game-changer. Modern buildings increasingly employ stay-put strategies, progressive evacuation plans, and multi-use spaces where simple evacuation isn't always the appropriate response. The 2025 revision recognises these realities and provides the framework to design systems accordingly.
Borrowed Light: No Longer Acceptable
A significant clarification is that borrowed light can no longer be relied upon to meet emergency lighting requirements. This has now been explicitly excluded from the scope of the standard.
For those unfamiliar with the term, borrowed light refers to illumination spilling into adjacent areas from emergency luminaires positioned elsewhere. While this might have been tolerated under previous interpretations, the 2025 edition makes clear that each space requiring emergency lighting must have dedicated provision. This reflects practical experience showing that borrowed light simply cannot be relied upon as a consistent source of illumination.
Enhanced System Resilience and Circuit Design
The standard introduces clearer requirements to improve system resilience and prevent single points of failure from compromising large areas of emergency lighting coverage.
A maximum of 20 luminaires can now be affected by a single fault on centrally supplied final circuits. This forces designers to think more carefully about circuit arrangement and distribution, ensuring that a single electrical fault doesn't leave vast areas without emergency lighting.
For high-risk task areas, the requirements are even more stringent. These spaces must have dual circuit supply from at least two separate circuits, providing redundancy where it matters most.
Cable routing has also received attention, with recommendations to route cables through low fire-risk areas wherever practicable. These changes collectively create more robust systems that are less vulnerable to common failure modes.
Photometric Verification: A New Ongoing Requirement
Perhaps the most significant operational change is the introduction of mandatory photometric verification. The standard now requires photometric verification every five years maximum, measuring actual light output and confirming that design requirements are still being met.
This goes well beyond the functional testing that most of us are familiar with. Photometric verification involves a proper illuminance survey, measuring actual lux levels across escape routes, at points of emphasis, and in task areas. It's a recognition that batteries degrade, luminaires age, and building modifications can affect lighting distribution in ways that simple lamp-testing cannot detect.
For facilities managers and building owners, this represents a new ongoing commitment. You'll need to budget for these surveys and ensure they're scheduled appropriately. For those maintaining multiple sites, coordinating these five-year cycles will require careful planning.
Updated Performance Requirements
The 2025 edition references the latest European standards (BS EN 1838:2024 and BS EN 50172:2024), bringing UK practice into alignment with international best practice. Key illuminance requirements include:
Escape routes require a minimum of 1 lux across the full route width, ensuring adequate visibility for safe movement.
High-risk task areas need a minimum of 15 lux or 10% of normal lighting (whichever is higher), achieved within 0.5 seconds. This rapid response time is critical for areas where delays could create immediate hazards.
Points of emphasis (including fire alarm call points, exit doors, firefighting equipment, and first aid posts) require a minimum of 5 lux vertical illuminance, ensuring these critical features remain clearly visible.
These aren't arbitrary numbers; they're based on extensive research into human visual performance under stress and emergency conditions.
Alignment of Definitions and Terminology
The standard has updated its definitions to align with BS 4422:2024 (Fire Vocabulary) and BS 9991:2024, creating consistency across the fire safety standards family. The definition of "competent person" has been harmonised, emphasising the need for suitable training, knowledge, practical experience, and proper instruction to carry out required tasks correctly.
Stricter Documentation and Variation Requirements
Within BS 5266-1, the term deviation has been replaced with variation. This reflects situations where the recommendations of the standard have been intentionally not followed because an alternative technical solution or practice has been adopted, and the standard now aligns the terminology with other standards such as BS 5839-1.
Like the recent updates to BS 5839-1, the 2025 revision of BS 5266-1 places greater emphasis on documentation and the formal recording of variations. Any departures from the standard's recommendations must be clearly identified in specifications and design proposals, making them obvious to all interested parties responsible for approval.
All variations must be documented in handover documentation, creating a clear audit trail. This protects everyone involved. Designers can demonstrate what was agreed, installers know what they're expected to deliver, and building owners understand exactly what system they're receiving and where it differs from standard recommendations.
Practical Implications for Self-Contained vs. Central Systems
An important clarification that will save confusion: self-contained luminaires do not require fire-resistant cables and can follow normal lighting circuit standards under BS 7671. Only central battery systems require the enhanced fire-resistant cabling that many installers have been uncertain about.
This distinction is significant because it affects both installation costs and design decisions. Self-contained systems benefit from simpler installation requirements, while central systems demand more robust infrastructure but offer centralised monitoring and maintenance advantages.
Who Needs to Act?
This update affects virtually everyone involved in building safety:
Designers and consultants need to familiarise themselves with the expanded scope and incorporate local area and standby lighting considerations into their specifications.
Electrical contractors and installers must understand the new circuit resilience requirements, the prohibition on borrowed light, and the distinction between self-contained and central system cabling requirements.
Facilities managers and building owners need to budget for the new five-year photometric verification requirement and ensure their maintenance contracts reflect these enhanced testing obligations.
Responsible persons under fire safety legislation should review their emergency lighting strategies, particularly if they operate buildings with stay-put policies or where evacuation isn't always the primary emergency response.
Building Control and regulators need to understand these changes when assessing compliance in both new builds and existing premises undergoing significant modification.
Looking Forward
The evolution from BS 5266-1:2016 to the 2025 edition reflects a maturing understanding of how buildings are actually used during emergencies. It acknowledges that modern evacuation strategies are nuanced, that building systems must be resilient, and that ongoing verification is essential to maintaining safety standards.
The alignment with European standards (EN 1838:2024 and EN 50172:2024) ensures that UK practice remains consistent with international best practice, beneficial for manufacturers, installers, and building operators working across multiple jurisdictions.
For those working with emergency lighting systems, now is the time to review your design templates, installation procedures, and maintenance protocols. The changes aren't merely administrative—they represent genuine enhancements to how we protect building occupants.
The withdrawal of the 2016 edition means that all new designs should now conform to BS 5266-1:2025. For existing systems, while wholesale replacement isn't mandated, any significant modifications or extensions should incorporate the new requirements where reasonably practicable.
The Bottom Line
BS 5266-1:2025 sets a higher bar for emergency lighting systems. The expanded scope, enhanced resilience requirements, and mandatory photometric verification all contribute to more robust, reliable systems that genuinely protect people when they need it most.
Emergency lighting has always been a critical life safety system. This revision ensures it evolves alongside modern building design, occupancy patterns, and emergency response strategies. By embracing these changes, we're not just ticking compliance boxes. We're actively improving the safety and resilience of the buildings we design, install, and maintain.
