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Types of system

Emergency lighting is normally required to operate fully automatically and give illumination of a sufficiently high level to enable persons of all ages to evacuate the premises safely. Most new buildings now have emergency lighting installed during construction, the design and type of equipment is normally specified by the relevant local authority, architect or consultant.

The British Standard provides the emergency lighting designer with laid down guide lines which form the general basis for him to work on. British Standard BS 5266: Part 1: 2005 includes in its scope residential hotels, clubs, hospitals, nursing homes, schools and colleges, licensed premises, offices, museums, shops, multi-storey dwellings etc. Although this standard recommends the types and durations of emergency lighting systems relating to each category of premise it should be remembered that the standards are minimum safe standards for the types of premises and that a higher standard may be needed for a particular installation.

Most emergency lighting schemes fall into one of the following categories:

• Non-maintained - The emergency luminaire units only illuminate in the event of a mains failure.
• Maintained - The emergency luminaire units are illuminated at all times using the same lamps for both normal and emergency operation.
• Combined - A luminaire comprising two or more lamps, one of which is energised by the normal supply and the other(s) energised by the emergency or unswitched supply and operational in non-maintained.

The type of system and emergency duration is often expressed in abbreviated form as per the following examples:

• M3 - Maintained System, emergency duration 3 hours.
• NM2 - Non-maintained System, emergency duration 2 hours.
• S1 - Combined System, emergency duration 1 hour.