Building Control Advice Sheet BC24
EMERGENCY LIGHTING
Issue No. 1 January 2010
EMERGENCY LIGHTING
Emergency lighting should be provided in the event of the supply to the normal lighting failing. It should be in all
areas where there is insufficient natural lighting at times that persons are on the
premises.
The illuminance of escape route signs is specified in BS EN 1030 : 1999 /
BS5266 - 7 1999, Clause 5.
The BS5206 - 8 2004 recommends that a maintained mode of operation should be
considered for illuminance of emergency escape, with signs in locations where
occupants may be unfamiliar with the building.
Escape Lighting Requirements
The role of emergency escape lighting is to reveal a safe passageway, fire alarm
call points, fire fighting equipment, escape signs and any permanent hazards
along the escape route.
Design consideration should be given to emergency lighting needs early in the planning stages of the premises, to
ensure that legal obligations are satisfied. Before finalising the plans it is essential to consult with the local enforcing
authority and ensure that local bylaws and interpretations are complied with.
In general, work places are used by persons who will be reasonably familiar with the layout and safety provisions for
an orderly evacuation in the event of an emergency. However, in laboratories and in continuous flow plans, some
processes may need terminating before evacuation.
In public places such as conference rooms, hotels and shopping centres, the majority of persons present are likely to
be unfamiliar with the layouts. It is, therefore, necessary to provide strategically placed escape signs permanently
indicating the ways out of areas and to see that adequate luminance is provided in special locations where a visual
task must be performed prior to evacuation.
Escape Route Signs
Much anxiety and confusion can be alleviated by strategically placed signs permanently indicating the ways out of
the premises.
It is very important that all exits used in an emergency are quite clearly signposted, and are visible at all times.
These should be illuminated with normal and/or emergency lighting systems. The signs should use the preferred
pictograms. On no account should signs be illuminated during emergency indicating 'NO EXIT'.
Where direct sight of an exit is not possible and doubts may exist as to its position, the direction signs with an
appropriate arrow should be added. The signs must direct someone unfamiliar with the building to the nearest exit.
The signs must comply with the requirements of BS5499 Parts 1, 2 or 3, and in one building should be uniform in
format and style.
The signs may be externally or internally illuminated. The use of radioactive self luminous signs is not recommended.
External signs with lettering of 50mm to 75mm high should be illuminated to at least 5 lux. The translucent white
facia of internally illuminated signs with lettering of 75mm to 125mm high should have luminance of 30 cd/m2.
Escape Route Illuminance
On the whole there are three types of areas to be considered for the purpose of escape lighting requirements :
a) Clearly defined routes, such as corridors and gangways.
The horizontal illuminance at floor level on the centre line of a clearly defined route should not be less than 0.2 lux
and the centre band 50% of the route width, up to 2 metres wide, should be lit to a minimum of 0.1 lux. Wider
routes may be treated as several 2 metre bands, but preferably as open areas.
b) Large open spaces, such as offices, supermarkets, dining halls, conference rooms, laboratories and 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 of an unobstructed floor should be not less than 1 lux, with
a uniformity of 0.025.
c) Areas having fixed seating, such as auditoriums, lecture halls and stadia. (These places will have a fixed seating
layout on either horizontal or sloping planes, but will be divided by gangways which are designed as clear escape
routes, and should be treated as such).
Any part of the area having a fixed seating layout the average horizontal illuminance, measured on a plane 2m
above floor/pitch level, should be not less than 0.1 lux, with a uniformity of 0.025.
Special Areas
In laboratories, and certain control rooms or work places, the activity may involve hazardous tasks not dependant on
electricity supply that will present a hazard if left in operation. These areas need to be made safe before evacuating
the area.
In these situations, the immediate area containing the task should be illuminated to a minimum luminance of 2 lux, or
such higher level that the task may demand. This illuminance may be of shorter duration than that used for escape
lighting. Often a strategically placed escape luminaire will suffice for this purpose.
Illuminance
All illuminance requirements are specified for direct light, i.e. exclude interflected
contribution. For uplights the first bounce is taken to be the direct value.
Operating Conditions
The emergency lighting must reach the required illuminance in 5 seconds after failure
of the supply to the normal lighting and should maintain these levels for at least 1
hour.
In certain locations, where staff are familiar with the premises, the response time may
be 15 seconds.
The emergency lighting luminaires should be chosen with care and be installed in locations where they will not cause
disability glare (dazzle).
System Choice
Basically, two systems can be considered for use. Central power or self-contained (single point).
In a central power system, the energy is provided by batteries or generators and the output is distributed through subcircuits to feed a number of luminaires. Typically, with a central battery system, the battery room or cubicle will
contain the charger, batteries, controls and indicators and the automatic change-over switches.
With a central system care should be taken on the location of the fault detection equipment or the supply of normal
lighting, so that sub-zone detection becomes effective.
Also, the wiring between the power source and the luminaires must be routed and protected by special means to
ensure operation integrity for the full working duration, even under fire conditions.
Central systems tend to be cheaper to purchase and maintain, but complex to install and extend. The luminaires
may use either incandescent or fluorescent lamps.
In a self-contained (single point with power pack not more than 1 metre from luminaire) system the emergency
luminaires are self powered and the luminaires operate independently in an emergency. Each luminaire is fully
equipped with a battery, a charger, a charge indicator and a change-over device. The batteries are continuously
charged via the normal unswitched local lighting circuit and ensures local detection.
Self-contained luminaires tend to be expensive, with the batteries having a restricted operating temperature, but are
easy to install and extend, and require little maintenance. It is well worth remembering that lives depend on
emergency lighting and therefore only reliable and safe equipment, meeting the current British Standard, should be
considered for use.
System Operation
Systems are classified according to categories and modes of operation.
Categories: The emergency lighting system can be designed to supply the required load for any desired time or
duration. However, for application in most premises, a duration of 1 hour is adequate. The duration is usually
designated by X/1, X/2, and X/3 for 1-hour, 2-hour and 3 hour rated units respectively.
Mode of Operation: The mode of operation is a description of the lamp working status in a luminaire. Broadly
speaking, there are two modes of operation, maintained and non maintained.
• Maintained - in this system the lamp is on all the time the premises are occupied. The lamps may be powered by
normal supply, directly or indirectly, and under emergency conditions they are automatically switched to the
emergency power. At all times, the output of the luminaire must meet the emergency lighting requirements.
• Non-maintained - in this system the emergency lamp is off when mains power is available to charge the batteries.
When the mains supply fails the lamp is energised from the emergency power source.
A variant of this system called 'combined' is often used where maintained lighting is required, such as internally
illuminated signs. The 'combined' system uses two lamps, one operated from the mains and the other, when required,
from the emergency power.
Maintained systems are identified by a marking of 'M', whilst the non-maintained is marked 'NM'. For most premises
the use of systems having designations of 'M/1' or 'NM/1' are adequate; that is 'maintained 1-hour' or 'non-maintained
1-hour'.
Inspection and Servicing
Regular inspection and servicing of emergency lighting schemes is essential.
BS5266 provides the framework for certification of completion of installation and certification for periodic testing and
servicing.
The onus for these activities falls on the owner / user of premises.
To verify that adequate emergency lighting is available at all material times, the system needs inspection / tests
daily, monthly, six-monthly and three-yearly. These may require only to check that the charge indicator is glowing,
showing battery charge, or that the lamp is maintained, exit sign is on. Testing may be made by automatic devices,
provided these give warning if action is required.
We hope that the above provides you with an insight into the concept and type of systems. Design of the system to
meet the minimum illuminance (lux) levels will be undertaken by the specialist designer. In most situations, the
actual levels provided far exceed the minimums stated in the BS/EN standards.