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EXTRACT FROM CIBSE
PUBLICATION:
The Fire Precautions Act, 1971 and the
Health and Safety at Work etc. Act of 1974 make it obligatory to provide
adequate means of escape in all places of work and public resort. 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.
ESCAPE
LIGHTING REQUIREMENTS
BS
5266, like most British Standards, is not
a legal requirement. However, it can acquire legal status by being adopted
as part of the by-laws. Although most enforcing authorities quote BS
5266, many modify the conditions. For example, they may insist on a
higher illuminance. In addition to this legal requirement, many organisations
have their own more onerous standards. Therefore, the designer must
thoroughly investigate the standards that apply to the building. 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 emphasise
the position of potential hazards, such as changes of direction, staircases,
changes of floor level and so on.
Fire equipment
- Fire fighting 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 illuminated to the same standard as the escape route to prevent
accidents.
For large open areas
- Offices, supermarkets, dining halls, conference rooms, laboratories,
multi-purpose 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 area, 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 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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