Fire Safety Glossary

BS 5266 is the British Standard that governs the design, installation, and maintenance of emergency lighting systems in the UK. Part 1 (BS 5266-1) covers non-domestic premises and specifies categories of emergency lighting, minimum illuminance levels, battery duration requirements, testing regimes, and the competence expected of installers and maintenance engineers.

Emergency lighting is a lighting system that activates automatically on failure of the normal mains supply, providing sufficient illumination to enable safe evacuation of a building. UK law requires emergency lighting in all non-domestic premises, and it must be designed, installed, commissioned, and maintained in accordance with BS 5266-1 by a competent person.

Maintained emergency lighting is a system in which the emergency luminaires remain illuminated continuously during normal mains operation and stay on — powered by their batteries — when the mains supply fails. It is typically specified in cinemas, theatres, and venues where sudden darkness would cause panic, and must be designed and maintained in accordance with BS 5266-1.

Non-maintained emergency lighting is a system in which the emergency luminaires only illuminate when the normal mains power supply fails. It is the most common type of emergency lighting installed in offices, industrial premises, and commercial buildings, and must meet the illuminance and battery duration requirements of BS 5266-1.