22 August 2006
EMERGENCY AND EXIT LIGHTING.
Introduction. The purpose of emergency lighting is to ensure the continuation
of illuminance along the path of egress from a building and provide adequate light for
the orderly cessation of activities in the building. The purpose of exit lights is to identify
the path of egress. Both types of lighting must be powered from both a normal power
source and an emergency source, with automatic switching from one to the other.
5-6.1.1 In some specific situations, emergency lighting might be required for specific
spaces or work areas that are not on the path of egress. There are often areas where
work of a critical nature must continue regardless of loss of normal power, such as a
computer mainframe room. In health care facilities, including hospitals, skilled nursing
homes, and residential custodial care facilities, lighting for the path of egress (including
exit signs) and elevator cabs is considered "life safety" lighting and must be connected
to the life safety branch of the facility's emergency power system. Task illumination at
anesthetizing locations, patient care areas, laboratories, intensive care units, recovery
rooms, and other locations as required by NFPA 70, Article 517 are considered "critical"
lighting and must be powered from the critical power branch of the facility's emergency
power system. In applications where the loss of light, even momentary, would
endanger personnel or risk other loss or damage, provide lighting systems to maintain
constant illumination through the use of an uninterruptible power supply of sufficient
capacity to permit an orderly cessation of activity. This lighting is in addition to path-of-
Figure 5-8. Typical exit sign.
Requirements for emergency lighting:
Although an elevator is not considered a component in the required
means of egress, all elevators must provide lighting in accordance with
ANSI A17.1 or ANSI A17.3 as applicable.
Where emergency lighting is required, arrange the system so that the
failure of any individual lighting element, such as the burning out of a light
bulb, cannot leave any space in total darkness.
Requirements for exit marking:
Lettering on all exit signs for an installation must be one uniform color.