Emergency lighting (EL) is lighting for a situation when the main power supply is cut and normal lighting fails. The loss of mains electricity could be the result of a fire or a power cut. Without this type of lighting it could lead to sudden darkness and possible danger to people.
EL is normally required to operate fully automatically and give light of a sufficiently high level to enable all people to evacuate the premises safely. Maintained or non-maintained is the principal consideration, which is decided by the use of the premises.
Maintained EL: a fitting in which the EL lamps are on at all times. EL Maintained mode is generally used in places of assembly such as theatres, cinemas, clubs and halls. The lights are typically dimmed when these premises are occupied and the emergency escape lighting prevents total darkness. EL Maintained fire exit signs are also used in public spaces for clear escape route.
Non-maintained EL: fitting whose lamps only come on when the power supply to the normal lighting fails. The time required to evacuate the premises depends on their size and complexity. The duration itself is dependent not only on evacuation time but also on whether the premises are evacuated immediately the power and normal lighting fails and are re-occupied immediately the supply is restored. The minimum duration of an emergency escape lighting system is 1 hour. That means that once the power supply fails, the luminaires must remain on for at least one hour. A minimum duration of 3 hours should be used for emergency escape lighting if the premises are not evacuated immediately, as in the case of sleeping accommodation, for example, or if the premises will be reoccupied immediately the supply is restored without waiting for the batteries to be recharged.