Most countries have statutory provisions that require the installation of emergency lights in all buildings exceeding certain sizes. These lights need to be provided at strategic locations throughout the building to assist in the evacuation of the building occupants during fire situations or other types of emergencies.
Picture 1 – Surface-mounted emergency light (EL light)
Picture 2 – EL light unit close up view
Picture 3 – Ceiling-recessed emergency light
Practically this emergency lighting is useful even without the emergency and during daytime.
Time gap between mains failure and standby generator supply
When the mains power fails, there is a certain time delay before the backup power supply can take over. The standby electric generator, the most usual form of backup emergency power in normal buildings, takes quite a few seconds to warm up before it can provide the electricity supply to essential services inside the building.
Windowless rooms and corridors can be dangerous
Some internal corridors in large buildings can be very dark without electric lighting. Serious accidents can happen if the corridor suddenly becomes dark. Even with a little stray lights from windows somewhere, the eyes take a little bit of time to adjust to the sudden change of light level.
Some internal rooms inside large air-conditioned buildings are totally windowless.
Even with windows, the daylight from outside the building may not reach the rooms.
During power failures, these rooms can be darker than nighttime out in the open air outside. At least outside there you can rely on a little light from the stars or the moon. Again, in this type of darkness, anything can happen.
Locations of the emergency lights
The self-contained emergency light fittings are usually installed at all exit routes and at all places where uninterrupted lighting is required. In the second situation this lights serve the dual functions of a fire related equipment and a normal lighting (with much reduced lighting level).
The emergency light fittings are connected to the essential supply of the building electrical system. This way the rechargeable storage battery is charged even during normal power failure (i.e. when the standby electrical generator is running).
The purpose of emergency lights
The self-contained emergency lights need to be provided at strategic places throughout the building in order to aid the evacuation of the building occupants out of the building in the event of failure of the mains supply.
The need for these emergency lighting is real even during daytime because some internal corridors inside the building are actually too dark without some form of lighting. The emergency lights are meant to provide the minimum brightness needed for a safe and orderly movement of the people.
Who is responsible for the design of the emergency lighting layout?
The exact quantity and the exact locations of these emergency light fittings are usually recommended by the Fire Department. In practice, a licensed architect is required by law to submit the building design plans to the Fire Department for approval before the building construction commences. The architect would need to incorporate these lighting into their fire protection design schemes in order to obtain the Fire Department’s approval.
Static Fire Protection System
This layout is part of what is normally called the “static fire protection”. Those services like the wet risers, etc are called active fire protection and they will need to be submitted by licensed professional mechanical engineers to the Fire Department after the passive fire protection schemes (submitted by the architects) have been approved.
Prior to the submission by the architect, the electrical engineer’s input may be requested by the architect with respect to the quantities and locations of the emergency lights.
However, this task has become so routine that the engineer’s advice on this aspect is rarely necessary.
After the approval has been obtained, the approved layout of the emergency lighting is binding and it has become an input and a minimum design requirement for the electrical engineer. She can add more of the emergency light fittings into the design, but she cannot omit or change what has been approved in the submitted drawings.
That is the principle behind the layout and locations of the emergency lighting fixtures.
General lighting on Essential Supply
In addition to the self contained emergency lights that are required by the fire department, some of the general lighting luminaries are also connected to the essential supply that has been backed by the standby generator.
This is sometimes done to supplement the lighting provided by the self-contained emergency lights. More often, however, this is done to provide some level of general lighting that can allow normal work to continue even in the event of normal power failure. Of course, power failures that are caused by fire conditions demand a different course of actions immediately from all the building occupants.
Self-contained lighted EXIT signs
One more lighting component that is closely related to the self-contained emergency lights is the lighted “EXIT” sign.
The Exit signs are also required by law similar to the emergency lights. They must be provided at all exit doors of all buildings and all floors, and at each location where the fire emergency exit routes change direction.
Similar to the emergency lights, these components of the building fire protection are included in the proposed static fire protection submitted by the architects to the Fire Department. An approved layout of this fire component will become a minimum design requirement to the electrical engineer. She can add more of the lighted Exit signs, but she cannot reduce them or change them.
Like the emergency lights also, the Exit signs are self-contained, battery operated. The difference between the two is that the Exit signs are always on.
The installation
The following pictures show how a ceiling-recessed emergency light is mounted to the ceiling panel.
Picture 4 – Side view of the ceiling-recessed emergency light installation
Picture 5 – Rear view, from above the ceiling panel, to show how it is fixed to the board
Picture 6 – Normal view
An emergency light is a very important standby equipment. Therefore, it should be regularly checked and tested. Fortunately, that is not difficult to do. Read this post, How To Test An Emergency Light, to know more.
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