Specific Techniques
6.4 Emergency lighting
Emergency lighting is provided when the supply to the normal
lighting fails. It helps people to see their way and move to
evacuate quickly to a safe place out of the building. It also
avoids panic, restores confidence and enables specific tasks to
be made safe.
Emergency lighting should be provided in all areas where,
when the normal lights fail, there is insufficient daylight or
borrowed light available for those people on the premises.
A risk assessment should be made to identify the places and
routes where people may be at risk and need evacuating in the
event of the normal lighting failing.
An emergency lighting scheme should be designed with
sufficient consideration to the type of premise, size, complexity,
kind of activities and type of people involved. Special
consideration should be given to places where the elderly and
those with disabilities may be present.
There are four main points to consider for an effective
emergency lighting scheme:
1 – Exit Signage
Visible safety signs and signage to indicate the escape
route and final exit should be available at all material times
(luminance of the sign’s safety colours must be at least 2 cd/
m²). The escape route signs must be located so that occupants
from any part of the premises can see and identify the direction
for evacuation.
2 – Mandatory Points
Emergency luminaires have to be carefully positioned to ensure
a compliant emergency lighting scheme. To provide adequate
illumination they need to be mounted close to potential hazards
on the route, such as stairs, a change of direction or crossings
and places requiring emphasis, such as first aid posts, fire
fighting appliances and marshalling points. Also for places
where people may need reassurance in the event the normal
lights failing, such as lifts, toilets or closets.
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3 – Illumination levels and infill lighting
In addition to the lighting of mandatory points, infill luminaires
may be required to achieve the correct lighting levels.
An adequate level of illuminance on the floor of escape areas
(minimum 0.5 lx) and escape routes (minimum on centre line
1.0 lx) should be made available within 5 seconds of the mains
failing to avoid anxiety, and remain operative for at least 1
hour, or longer if required, for safe evacuation. Additionally
take care to illuminate the volume of space (from floor up to a
height of 2.0m) through which people move during evacuation
by mounting luminaires above head height.
High-risk task areas should be illuminated to an adequate level
(minimum 15 lx) within 0.5 seconds of the normal lights failing
for as long as required to complete making the task safe or
whilst people pass by if it is by the escape route.
Illumination should be carried out with light sources having a
colour rendering index of at least Ra 40 so that safety colours
in an escape area or on an escape route can be seen and
discriminated.
Stylish luminaires should be chosen to blend in with the
design of the overall lighting scheme, but they must suit the
environmental conditions of the location. For example use
IP65 emergency lighting luminaires outside the final exit. The
luminaires may be dedicated standalone types or integrated
into standard lighting luminaires. They can be self-contained or
central power fed depending on the size and complexity of the
premises, the operation and servicing and practicalities and
through life economics of the installation.
4 – Maintenance and testing
Once the scheme is installed and commissioned, it is essential
that the luminaires are properly maintained and ready to perform
in the event of an emergency. To make sure installed emergency
products are always fit for purpose, regular testing has to be
conducted by the building operator. Therefore consideration
should be given at the design stage to the intended method
- be it local switch, automatic self-testing or an automatic
remote/central controlled testing system. Also assess and plan
a schedule for servicing the lamps and batteries at required
intervals. Finally, remember the commissioning and certification
requirements for both the design and the installed scheme.
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Emergency lighting system considerations
Standby lighting is used as an alternative to normal lighting but
it can also form the emergency escape lighting solution. When
it does it must follow the rules governing escape lighting.
Escape lighting covers the need for clearly defined escape
routes in the premises formed by corridors or paths indicated by
painted lines. Open areas are defined as places where there
is no clear route or where the routes are changing such as a
large shop, open plan office or multi purpose hall. A high-risk
task area is where some uninterruptible activity is ongoing,
such as a chemical dip process, or some other process that
requires unbroken lighting conditions for safe shut down. In
some places where there is high risk of smoke accumulation
(airlines, passenger ships) low location way guidance systems
are provided to supplement the escape route lighting.
Emergency Lighting
Emergency escape lighting
Escape route lighting
Standby lighting
Open area (anti-panic) lighting
High risk task area lighting
Low location way guidance
Fig. 6.18 Specific forms of emergency lighting
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Clearly defined escape routes
Clearly defined escape routes are taken to be up to 2m wide.
Here the horizontal illuminance at floor level on the centre line
should be not less than 1 lux, and the centre band of at least
50 per cent of the route width should be illuminated to at least
half the centre line value. The diversity of illuminance should not
exceed 40:1. Wider routes may be treated as 2m wide strips
of escape routes but preferably as open areas. The design
illuminance is to be provided within 60 seconds, but preferably
within 5 seconds of the supply failure. To avoid dazzling
people it is important not to exceed the intensity limits related to
the mounting height of the luminaires.
50% of width
not less than 0.5 lx
not less than 0.5 lx
not less than 1.0 lx along centreline
Fig. 6.19 Escape route plan (up to 2m wide)
Safety signs
Strategically placed signs permanently indicating the escape
directions from the premises are essential to alleviate anxiety
and confusion by the people present. The signs should conform
to the graphic design, colour and luminance criteria given in
the EN1838 standard. It is important that during an emergency
only signs that give a positive indication to the way out should
be illuminated and that the signs are mounted high enough
(above 2.0m) so that they are not obscured.
Open areas
Areas where the furnishing or equipment on the floor is
frequently reconfigured will not have clearly defined escape
routes and are therefore treated as open areas, as defined
above.
In these the illuminance on the floor should be a minimum
0.5 lux anywhere up to 0.5m from the walls and 50 per cent
should be provided within 5 seconds, 100 per cent being
provided within 60 seconds of the normal lights failing. The
diversity of illuminance should not exceed 40:1. To avoid
dazzling people the intensity limits for the luminaire should not
be exceeded for the mounting height in the scheme.
Exit signs should be located so that they are visible from any
part of the space.
Large areas require
min 0.5 lx up to
border of 0.5m
of the perimeter
area. Max. to min.
illuminance
ratio not greater
than 40:1.
Exit sign
must be
visible from
all parts
of open area
Fig. 6.20 Escape route illuminance requirements
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High risk task areas
During the failure of the normal lighting supply, emergency
lighting is required in places where machinery, plant or other
processes may present a hazard if left in operation, and that
must be shut down before evacuating the area, In some cases
the escape route may be alongside these hazardous tasks
and therefore needs to be highlighted. There are also places
where the task activity cannot be halted and needs standby
emergency light (such as in an operating theatre).
The high risk tasks areas should be illuminated as required by
the task and in any event the maintained illuminance should
be not less than 10 per cent of the required maintained
illuminance for that task and should not be less than 15 lux and
be available in full within 0.5 seconds. The uniformity should
not be less than 0.1. For this a no-break or maintained system
should be considered.
Power systems for emergency lighting
Emergency lighting systems are usually powered from batteries
or generators that are automatically triggered by a detection
system as soon as the mains system fails. The system duration
or category is defined by the period the system is able supply
power to the load. Usually given as 60 minutes (1 hour) or 180
minutes (3 hours). The two main types of electrical systems in
use are self-contained and central power:
Self-contained systems
Each luminaire is equipped with battery, charger, indicator
and changeover device. These elements may be integral to the
luminaire or housed in a separate unit mounted less than 1m
from the luminaire. The mains supply charges the battery, which
cuts in when the mains system fails. Self-contained systems are
easy to install and extend, and require minimal maintenance.
The system may include a self- testing facility that can carry
out the routine monthly and annual operational tests and give
local indications of the status. They can also be connected to a
central managed automatic testing system and can give printed
report of any defects.
Each luminaire is equipped with batteries and
inverter to power one lamp on mains failure
The gear may be remote mounted, if so the box
should be within 1m of the luminaire.
Fig. 6.21 Self-contained system
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Central systems
Here the power is provided by remote central batteries or
generators and is distributed through sub-circuits to a number
of slave luminaires. These systems are best suited for large
premises. They will require space to house the large battery
sets or generator. The wiring of the sub-circuits has to be
protected and be of high-integrity. During design due allowance
should be made for voltage drops. As part of the high
integrity considerations the luminaires with loop-in/out wiring
facility must also have protected glands and terminal blocks,
alternatively the luminaires may be treated as an individual spur
connection to a protected emergency power ring sub-circuit.
The system must include monitoring of the mains supply and
detection of failure of local circuits in each part of the premises
to bring on the emergency lighting.
Fig. 6.22 Central system
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Fig. 6.23 Summary of modes of operation
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Maintained (M)
The lamp is lit at all material times and is powered by the mains
supply under normal conditions. In an emergency, when the
mains fail, an emergency power source cuts in to power the
lamp.
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Combined (C)
This is a variant of the maintained luminaire in which one lamp
is powered by the mains supply during normal conditions.
A second lamp operates only under emergency conditions
powered by an emergency power source. This type of
luminaire provides light at all material times and is best suited
for signage.
Planning Schemes
The lighting calculations involved in emergency lighting are
straightforward. It is important to base all calculations on real
photometric data for the specific lamp and luminaire, with the
output in the worst (minimum) condition. The EN 13032-3
European standard gives the format of the photometric data and
defines the critical factors for to be used in calculations.
Planning Sequence
There is no precise sequence to be followed, but this
checklist indicates a possible course. (It is most important that
consultation with relevant bodies over the specific plans is
carried out early in the design process).
1. Establish licensing requirements
2. Examine building plans
3. Mark exits and final exits
4. Mark escape routes
5. Identify open areas and special locations
6.Mark location of hazards, fire-fighting appliances, and
alarm call points.
7. Identify small toilets with no windows and toilets over 8m².
8. Identify closets, control rooms, special plant rooms and lifts
9. Note illuminance and other specification requirements.
10. Select signs and escape luminaires fit for the purpose.
11. Position luminaires at essential locations.
12. Add extra luminaires to complete scheme.
13. Check uniformity and glare.
14. Prepare installations instruction.
15.Prepare commissioning procedure, including illuminance
checks.
16. Prepare operation testing service instructions.
17. Prepare logbook.
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Inspection and Servicing
Regular inspection and servicing of emergency lighting
schemes is essential. In the scheme design these matters must
be considered and adequately documented. The standards EN
1838 and EN 50172 provide the framework for certification
of completion of installation and certification for periodic
testing and servicing. The onus for these activities falls on the
competent person of the owner/user of premises. Any faults
noticed should be recorded in the logbook
To verify that adequate emergency lighting is available at all
material times the system needs to be inspected and tested
monthly and to make full duration tests annually. At the end of
each test the circuit is restored to charge conditions and the
charge indicator should glow to show that the battery is on
charge. The inspection needs to confirm that the luminaires
are in place as designed, the lamp in maintained luminaires
is functioning and the signs are visible. The testing may be
made by automatic systems but these must provide noticeable
feedback and warning if action is required.
Servicing considerations are straightforward. The batteries or
fuel tank for the generator may need topping up. The luminaires
need cleaning, failed lamps changing and the batteries
in self-contained luminaires replaced at the manufacturers
recommended interval. Regular servicing will keep the systems
effective and reliable for operation at all material times.
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