The LWF Blog

Fire Safety for Facilities Management Personnel – Emergency Escape Lighting – Part 169

September 26, 2022 10:40 am

Lawrence Webster Forrest (LWF) is a specialist fire engineering and fire risk management consultancy whose aim is to give information on best practice in fire safety for facilities management personnel through this blog series. In part 168, LWF discussed Central Battery Emergency Escape Lighting Systems before considering Emergency Generators. In part 169, we look at the modes of operation of luminaires and the duration of emergency escape lighting.

Luminaires have three possible modes of operation, as follows:

Non-maintained – the luminaire operates only when the normal lighting system fails

Maintained – the luminaire is illuminated at all times

Combined – (maintained or non-maintained) one lamp in the luminaire becomes operational when energized by the emergency supply when normal supply fails, the other lamp is energized from the normal mains supply

Maintained and non-maintained does not refer in any way to the maintenance schedule for the lighting system, it refers only to the mode and method of lighting.

Illuminated exit signs are usually lit at all times, either by the maintained or combined maintained methods. Maintained emergency escape lighting is commonly provided in cinemas, theatres, concert halls, nightclubs or any place of public assembly where the lights are habitually lowered.

Duration of emergency escape lighting

BS 5266-1 Code of Practice for Emergency Lighting recommends a duration of 1 or 3 hours for emergency escape lighting depending upon the type of occupancy.

In premises where people might sleep or be largely unfamiliar with their surroundings – cinemas, theatres, sports venues, public houses, restaurants etc. 3 hours duration is recommended.

In other premises, such as offices, shops, some factories, a 1 hour duration is considered acceptable.

Although a 1 hour duration system might be sufficient for some occupancies, in practice, 3 hour systems are often installed in those too. The reasoning is purely practical and based on the fact that the building need not be evacuated if there is a total power failure that does not exceed 2 hours in duration and allows for the immediate reoccupation of the building. A 1 hour system would require the system to be recharged before it could be occupied again. In most businesses, a cessation of activity to allow the system to be recharged would be more costly than installing the 3 hour system in the first instance.

In part 170 of this series, LWF will discuss the siting of luminaires. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact LWF on freephone 0800 410 1130.

 

Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 25 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.

 

While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.