Emergency Lighting to BS 5266: Durations, Coverage & Common Mistakes
Lighting · 7 July 2026 · For contractors and project engineers
Emergency lighting isn't ordinary lighting with a battery — it's a life-safety system with its own standard, BS 5266, and it's where lighting designs most often come unstuck at building control. Here's what it actually has to achieve, and the mistakes that get designs sent back.
What Emergency Lighting Has to Do
When the normal supply fails, the emergency lighting has to let people leave safely and find the safety equipment on the way out. That breaks into three jobs: light the escape routes, provide open-area (anti-panic) light so people can reach a route, and cover high-risk task areas where a sudden loss of light would be dangerous. Each has its own illuminance target.
Durations: One Hour or Three?
The system has to run on its own power for a defined duration. Three hours is usual where people sleep on the premises, where the building is used by the public, or where it won't be re-occupied only after a full recharge. One hour can be acceptable where the premises are evacuated immediately on failure and not re-occupied until the batteries have recharged. The occupancy drives the choice — get it wrong and the whole system is the wrong size.
Coverage Is About the Floor, Not the Fitting
The requirement is a minimum illuminance on the ground, not a fitting every so many metres. As a guide, escape routes need a minimum along the centre line (commonly 0.5 lux), open (anti-panic) areas a minimum across the core of the space, and high-risk task areas a much higher level tied to the normal task lighting. Just as important are the points of emphasis that must have a luminaire near them: every exit door, stairs and changes of level, direction changes, fire-alarm call points, firefighting equipment and first-aid points.
Maintained or Non-Maintained, Self-Contained or Central
Maintained fittings are lit all the time (common in public spaces); non-maintained only come on when the mains fails. Power is either self-contained (a battery in each fitting) or from a central battery system. Each has cost, maintenance and fire-survival implications — a central system, for instance, brings the supply cabling into scope for fire-rated support (see BS 8519 supports).
Where Designs Go Wrong
- Spacing fittings from a manufacturer table instead of calculating illuminance on the actual layout.
- Missing points of emphasis — exits and stairs with no dedicated luminaire.
- Choosing the wrong duration for the occupancy.
- Using the luminaire's rated output rather than its reduced output at the end of the rated duration.
- Ignoring uniformity, so the route has bright pools and dark gaps.
What This Means for Your Design
A proper emergency lighting design is a calculation on the real geometry, not a spacing rule of thumb. Our DIALux lighting design service produces emergency illuminance calculations and coverage checks to BS 5266, with the points of emphasis marked up — ready for building control and the fire strategy.