Non-Maintained vs Maintained Emergency Lighting
The two primary modes of emergency lighting operation are:
• Non-maintained — the emergency luminaire is OFF during normal operation. It only switches on when mains power fails, using its internal battery to provide illumination for a minimum duration (typically 3 hours in the UK). When mains power is restored, the luminaire switches off and the battery recharges. These are identified by a 'non-maintained' or 'NM' label.
• Maintained — the emergency luminaire is ON at all times, functioning as normal room lighting during mains operation AND as emergency lighting during a power failure. When the mains fails, the luminaire seamlessly switches to battery power. Maintained fittings are required in areas that are always lit when occupied, such as cinema auditoria, theatre halls and some hospital areas.
When is Non-Maintained Required?
Non-maintained emergency lighting is the most common type installed in UK commercial buildings. It is used in:
• Escape routes — corridors, stairways and passageways that are normally lit by separate mains-powered luminaires. The non-maintained emergency fittings only activate if those mains luminaires fail. • Open areas — large open-plan spaces (over 60m²) where non-maintained fittings provide anti-panic illumination during power failure. • High-risk task areas — locations where sudden darkness could cause immediate danger (machinery, chemical processes).
The advantage of non-maintained is simplicity and cost — the emergency fittings don't need to provide everyday illumination, so they can be smaller, lower-output and less visually intrusive.
When is Maintained Required?
Maintained emergency lighting is mandatory in locations where the emergency fitting IS the primary light source, or where lighting must remain continuously on:
• Toilets and washrooms exceeding 8m² floor area • Cinema auditoria and performance venues (lighting must never be fully off when occupied) • Sleeping accommodation escape routes (hotels, care homes, hospitals) • Any area where non-maintained fittings would not be visible when the general lighting is on (e.g. exit signs — these must be permanently illuminated)
Most exit signs in the UK are maintained — they display the running man pictogram at all times, not just during a power failure.
UK Standards and Testing
Emergency lighting in England and Wales must comply with:
• BS 5266-1 — Code of practice for emergency lighting • BS EN 1838 — Lighting applications: emergency lighting (minimum illuminance values) • The Regulatory Reform (Fire Safety) Order 2005 — places a legal duty on the 'responsible person' to ensure adequate emergency lighting
Key requirements: • Minimum duration — 3 hours for most premises, 1 hour for specific cases • Minimum illuminance — 1 lux along escape route centre lines, 0.5 lux in open areas • Monthly functional tests and annual full-duration discharge tests are mandatory • Self-test emergency luminaires with DALI integration can automate test scheduling and reporting, reducing compliance burden
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