When the mains fails,
the way out stays lit.

The rated duration for most premises is three hours, which is what BS 5266-1 expects wherever a building might be reoccupied soon after an evacuation or where escape could be slow or phased. A one-hour duration is permitted in limited cases, but only where the premises are evacuated immediately and stay empty until the batteries have recharged, which is a hard operational promise to keep. In practice three-hour fittings are the norm and what fire risk assessors and insurers expect to find. The duration is only real if it’s tested, which is exactly what the annual full-duration test exists to prove.

BS 5266-1, alongside BS EN 50172 / BS 5266-8, sets the regime: a brief monthly function test of every luminaire and internally illuminated exit sign to confirm it lights when the supply is interrupted, and an annual test for the full rated duration, usually three hours, to prove the batteries still hold their charge. Central battery systems also need their indicators checked daily, which is a walk-past rather than a test. Every result is recorded in the fire safety logbook, because under Article 17 of the Fire Safety Order the maintenance record is the evidence, and an untested system reads as an unmaintained one.

Because the test works by discharging the batteries, and they can take up to 24 hours to recharge to full capacity. Run it on a normal Monday morning and the building spends the rest of the day with little or no emergency cover if the mains genuinely fails. The answer is to run the full-duration test at a time of low risk: the start of a weekend closure or shutdown, or out of hours in a building that empties. In premises that never empty, luminaires can be tested in alternate groups so cover is never wholly lost. It’s a planning question as much as an electrical one, and it’s the kind of detail a testing contract exists to get right.

A non-maintained luminaire stays off in normal conditions and lights only when its supply fails, which suits most workplaces where the normal lighting is on whenever people are in. A maintained luminaire runs all the time and keeps running on battery through a failure; it’s specified where occupants are unfamiliar with the building or the lighting is deliberately low, such as cinemas, theatres and licensed venues. Exit signs are often maintained in any case, so the sign is always visible. The choice is made space by space in the BS 5266-1 design, not per building, and getting it wrong is one of the commoner findings in our first survey of an estate.

SP203-4 is BAFE’s third-party certification scheme for emergency lighting systems, structured like SP203-1 for fire alarms: four modules covering design, installation, commissioning and maintenance, audited by a UKAS-accredited certification body (BSI, NSI or SSAIB) rather than by BAFE itself. No law forces your contractor to hold it, but third-party certification is the recognised benchmark of competence under the Fire Safety Order, and specifying it costs one line in a tender. Gemini AMPM holds SP203-4 registration under Registered Organisation ID 302260, verifiable on the BAFE register in about two minutes.