Civil Engineering Reference
In-Depth Information
Table 9.9
Provision of emergency escape lighting
escape signage. The choice of fi tting will be dependent
upon the:
Areas needing emergency escape lighting
➤
Size and nature of the space to be illuminated
➤
Use of the building
Each fi nal exit door including both internal and external
routes
➤
Type of occupancy.
All escape routes including those that may assist persons
making their way from the building to the assembly point
For some larger buildings the power for emergency light-
ing may be provided by a generator or central battery
system. In all other cases emergency lighting is provided
by self-contained units. Emergency lighting luminaries
are categorised according to the following aspects of
their design:
Intersections of corridors (should also assist in illumination of
emergency exit signage)
Any change in direction or fl oor level, including temporary
partitions, ramps, steps or ladders
All stairways to ensure each fl ight and landing is provided
with adequate illumination
➤
Whether they are illuminated under normal con-
ditions (referred to as being maintained) or only
operated on the failure of the normal power supply
(non-maintained)
Windowless rooms and WCs that exceed 8 m
2
Disabled WCs
➤
Whether they form part of a normal light fi t-
ting (referred to as combined) or are free standing
(satellite)
Areas needing emergency lighting
Fire fi ghting equipment and fi re alarm call points - fi re
points
➤
Whether the emergency illumination is provided by
the same bulb or fi lament that is illuminated under
normal conditions (compound).
Hazardous plant and equipment - needing isolation in the
event of an emergency
Lift cars
BS 5266 Part 1: 2005 categorises emergency light-
ing units by their type, mode of operation, facilities and
duration of emergency lighting it will provide. Table 9.10
summarises the various aspects of the categorisation of
emergency escape lighting units and their codes.
Using a combination of the codes and some prose
suggested by BS 5266, individual emergency lighting
units are now described by the various aspects of their
design in relation to each of the categories. The full
description of a particular unit can then appear as a
code. This allows easy specifi cation of units during the
design stage of a system and also allows the character-
istics of individual units to be easily identifi ed once they
have been installed. For example, a luminaire conform-
ing to BS 5266:2005 that is self-contained, which only
operates when the normal power supply fails, has a local
test facility and is designed to operate for 3 hours will be
described as in Figure 9.52.
The specifi cation, design and installation of
emergency lighting systems require competence in fi re
safety, physics and electrical engineering. Calculations
relating to the level of lux falling on the centre line of
the means of escape that take into account the natural
luminescence of the surrounding building and decorat-
ing materials are complex.
It is of course possible to apply 'rules of thumb'
to the provision of emergency lighting; however, once
a system has been installed it must be certifi ed by a
competent engineer that it fully satisfi es the require-
ments of BS 5266:2005.
Halls and other areas exceeding 60 m
2
Fire alarm panels
escape, etc. to be used at all times. The amount of
light that falls on a surface is referred to as 'luminance'.
Luminance is measured in lux (lx). The standard that is
normally considered acceptable for escape routes is
between 0.2 and 1 lx.
For example, for routes that are normally clear as
in the case of corridors and stairways, the minimum
luminance on the centre line of the route at fl oor level
should be 0.2 but 1 lux is considered preferable.
In all cases emergency lighting should activate
within 5 seconds of the failure of power to the normal
lighting circuit. The emergency lighting will then continue
to operate for a specifi ed period of time, typically 3
hours, but sometimes less.
Types of luminaries
The required level of luminance for
emergency escape
lighting
can be provided in a number of ways using a
variety of light fi ttings. Individual emergency lighting
units can be self-contained, integrated into a stand-
ard light fi tting or provided as an integral part of fi re
