Beam Lighting Engineering

Emergency Lighting

Emergency lighting is an essential part of this requirement. BS 5266, the code of Practice for the Emergency Lighting of Premises, lays down minimum standards for the design, implementation and certification of emergency lighting installations. Emergency lighting is lighting provided for use when the main lighting fails for whatever reason. There are two types; escape lighting and standby lighting. Escape lighting is provided to ensure the safe and effective evacuation of the building. It must; (a) indicate clearly and unambiguously the escape routes; (b) illuminate the escape routes to allow safe movement towards and out of the exits; (c) ensure the fire alarm call points and fire equipment provided along the escape route can be easily located. Some building areas cannot be evacuated immediately in the event of an emergency or power failure. This is often because life would be put at risk; for example, in a hospital operating theatre, or in some chemical plants where shut down procedures must be used. In these circumstances, appropriate activities must be allowed to take place and standby lighting is required. The level of standby lighting will depend upon the nature of the activities, their duration and the associated risk. Standby schemes may be to provide from 5% to 100% of the design service illuminance according to circumstances. In some cases the lighting requirements may be more demanding in the event of power failure. Correct lighting requirements can only be established by careful analysis. Standby lighting can be regarded as a special form of conventional lighting and dealt with accordingly. Escape lighting requires different treatment.

Marking the route
All exits and emergency exits must have exit or emergency exit signs. Where direct sight of an exit is not possible, or there could be some doubt as to the direction, then direction signs with an appropriate running man pictogram and the words exit or emergency exit are required. The idea, is to direct someone who is unfamiliar with the building to the exit. All of these signs must be illuminated at all reasonable times so that they are legible.

Illuminating the route
The minimum illuminance along the centre line of a clearly defined escape route should be 1 Lux. The emergency lighting must reach its required illuminance 5 seconds after failure of the main lighting system. If the occupants are familiar with the building, this time can be increased to 15 seconds at the discretion of the enforcing authority.

Other important factors are:

Glare – The emergency lighting luminaires should not cause problems of disability glare.

Luminaires should be mounted at least 2m above floor level in order to avoid glare but should not be too high or they may become obscured by smoke.

Exits and changes of direction – Luminaires should be located near each exit door and emergency exit door and at points where it is necessary to emphasize the position of potential hazards, such as changes of direction, staircases, and changes of floor level and so on.

Fire equipment – Firefighting equipment and fire alarm call points along the escape route must be adequately illuminated at all reasonable times.

Lifts and escalators must be illuminated – Although these may not be used in the event of fire they should be illuminated. Emergency lighting is required in each lift car in which people can travel.
Escalators must illuminate to the same standard as the escape route to prevent accidents.

For large open areas – Offices, supermarkets, dining halls, conference rooms, laboratories, multipurpose rooms, these places will not have defined routes and the layout of furnishing may change from time to time. The average horizontal illuminance over the whole area on the unobstructed floor should not be less than 1 lux.

Special areas – Emergency lighting luminaires are required in all control rooms and plant rooms. In toilets of over 8m2 gross areas, emergency lighting should be installed to provide a minimum of 1 lux.

High risk areas – Areas containing rotating machinery etc… In these areas emergency lighting should be provided at 10% of the normal illuminance level or 15 lux, whichever is the greater.

Exit Signs – BS5266 specifies the use of the plain EXIT legend, however European legislation now calls for running man pictograms. During the transitional period, up to Jan 1996, there is no requirement for the UK to change all installed exit boxes, however any additionally required exit signs within the same building must be of the same format. After this date the running man pictogram will be mandatory, with the requirement of a global change in all buildings.

Planning sequence
When planning an emergency lighting system the following sequence will help:
1. Define the exits and emergency exits.
2. Mark the escape routes.
3. Identify any problem areas. For example, areas that will contain people unfamiliar with the building, plant rooms, escalators, etc.
4. Mark the location exit signs. These can be self illuminated or illuminated by emergency lighting units nearby. Mark these onto the plan.
5.Where direction signs are required mark these and provide necessary lighting.
6. Identify the areas of the escape route, paying particular attention to stairs and other hazards.
Remember to allow for shadows caused by obstructions or bends in the route.
7. Add extra luminaires to complete the lighting of the escape route, paying particular attention to stairs and other hazards. Remember to allow for shadows caused by obstructions or bends in the route.
8. Add extra luminaires to satisfy the problem areas identified in item 3 of this sequence.
Make sure that lighting outside the building is also adequate for safe evacuation.
9. Check that all fire alarm call points and fire equipment have been adequately dealt with.

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