Emergency Lighting Explained: BS 5266, Maintained vs Non-Maintained, and Testing

When the mains fails, people still need to find their way out. That is the whole purpose of emergency lighting, and in the UK it is not optional: the Regulatory Reform (Fire Safety) Order 2005 in England and Wales, and its equivalents in Scotland and Northern Ireland, place a duty on the "responsible person" for a building to ensure that escape routes are adequately lit if the normal lighting fails. The detail of how to do that is set out in a family of standards headed by BS 5266-1, the code of practice for emergency lighting, alongside BS EN 1838, which defines the light levels, and BS EN 50172 / BS 5266-8, which covers systems and testing.

What has to be lit, and how brightly

BS EN 1838 divides emergency lighting into escape route lighting, open area (or anti-panic) lighting, high-risk task area lighting and standby lighting. On a defined escape route, the minimum is 1 lux along the centre line at floor level; in open areas over 60 m², 0.5 lux over the core of the floor; and in high-risk task areas — where a process must be shut down safely — 10% of the normal illuminance or 15 lux, whichever is greater. Points of emphasis such as changes of direction, stairs, fire alarm call points, fire-fighting equipment and final exits must be individually lit. Exit signs follow BS EN ISO 7010 pictograms and BS EN 1838 sets their viewing distances.

Duration is the other headline figure. In the UK the norm is three hours. A one-hour system is only permitted where the premises will be evacuated immediately on failure of the supply and not reoccupied until the batteries have recharged — which rules it out for most buildings people sleep in, and most where they might return quickly.

Maintained, non-maintained, and the variants between

A non-maintained emergency luminaire is off in normal conditions and switches on only when the mains fails. It is the common choice for general escape-route lighting in workplaces, where the normal lighting is on whenever the building is occupied. A maintained luminaire is lit at all times, from the mains normally and from its battery in an emergency; this is required for exit signs and is the usual choice in places of assembly — theatres, cinemas, nightclubs — where the normal lighting may be dimmed or off while people are present. A combined or sustained fitting contains two light sources, one for normal lighting and one for emergency. Most modern LED luminaires can be supplied with an integral emergency pack that converts a standard fitting into a non-maintained or maintained emergency version, which is why the option appears on so many datasheets.

Behind the luminaire sits the power source. Self-contained fittings carry their own battery and charger and are simple to install and extend. Central battery systems feed many luminaires from one battery bank, which simplifies testing and battery replacement in large buildings at the cost of fire-rated wiring back to the central unit. Battery chemistry has moved from nickel-cadmium through nickel-metal-hydride to lithium iron phosphate, which offers longer life and better tolerance of the warm environment inside a luminaire; a design life of four years for the battery is a typical expectation whatever the chemistry.

Testing: the part that gets forgotten

An emergency luminaire that has not been tested is a hope, not a system. BS EN 50172 requires a monthly function test — a brief simulated mains failure, long enough to confirm every luminaire and sign lights — and an annual full-duration test, in which the system runs for its full rated three hours and every fitting is confirmed to still be lit at the end. Central battery systems also need a daily visual check of the indicators. Results go in a logbook, which the fire risk assessor and the fire service are entitled to see. Because the annual test leaves the batteries flat, it should be scheduled for a time when the building is unoccupied or the risk is otherwise controlled.

Self-test luminaires carry out these tests automatically and show the result on an indicator LED, which removes the labour of walking the building with a key switch but not the duty to read and record the results. Addressable systems — often using DALI emergency devices — report the results centrally and are increasingly the default in larger new buildings.

The specifier's checklist

• A design to BS 5266-1 by a competent person, showing escape routes, points of emphasis, open areas and any high-risk task areas, with luminaire positions and spacing data from the manufacturer.
• Three-hour duration unless the one-hour exemption clearly applies and is documented.
• Maintained fittings for exit signs and places of assembly; non-maintained is acceptable for most workplace escape routes.
• Luminaires and conversion kits certified to BS EN 60598-2-22, the luminaire safety standard specific to emergency lighting.
• A testing regime — monthly and annual — with a named person, a logbook and, ideally, self-test or addressable fittings to make it sustainable.
• A completion certificate at handover and a record of the design, so that the fire risk assessment has something to refer to.

Emergency lighting is judged on the one night it is needed. Everything in the standard exists to make sure that, on that night, it works.

For most buildings none of this is expensive relative to the rest of the electrical installation, and the emergency variant of a standard LED fitting adds modest cost. What it does require is that someone owns it: a design at the start, the right fittings in the right places, and a testing routine that actually happens. If a building has emergency fittings but no logbook, the first of those steps was done and the last was not — and it is the last one that the fire risk assessment will ask about.