Mode of operation of Emergency luminaire
Maintained or non-maintained is the principal consideration, which is decided by the use of the premises.
Maintained emergency luminaire: a luminaire in which the emergency lighting lamps are on at all times.
Maintained mode is generally used in places of assembly such as theatres, cinemas, clubs and halls; the full list is contained in BS 5266. The lights are typically dimmed when these premises are occupied and the emergency escape lighting prevents total darkness.
Maintained fire exit signs are also used in public spaces even where these are well lit to offer clear escape route guidance in evacuation situations where the power does not fail.
Non-maintained emergency luminaire: a luminaire whose emergency lamps only come on when the power supply to the normal lighting fails. Non-maintained is the typical mode in a workplace or similar environment in which artificial lighting is normally deployed while the premises are occupied.
Combined emergency luminaire: a luminaire containing two or more lamps, at least one of which is energized from the emergency lighting supply and the other(s) from the normal lighting supply. A combined emergency luminaire can be either maintained or non-maintained. These are also called switchable emergency lights.