The installation of self contained emergency lights is a statutory requirement in most countries. They 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 o 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 illuminance needed for a safe and orderly movement of the people.
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 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.
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 basically the principle.
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 caused by fire conditions demand a different course of actions immediately from all the building occupants.
There is one more lighting component that is closely related to the self contained emergency lights, that is the “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 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.
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