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Emergency lighting is a staple of most all non-residential buildings. Areas covered by the National Fire Protection Association (NFPA) life safety code addressing emergency lighting for egress from buildings or structures include designated stairs, aisles, corridors, ramps, escalators and passageways leading to an exit.
According to the NFPA, whenever illumination changes from one energy source to another in response to a power outage (whether the standby source of power is supplied by generator, inverter system, central rechargeable battery unit or individual rechargeable battery), there should be no appreciable interruption of illumination during the changeover. The emergency lighting should last for a minimum of 90 minutes and, through spacing of the fixtures and other guidelines, needs to satisfy initial footcandle requirements and allowable declining illumination. The emergency lighting system has to either operate continuously or be capable of repeated automatic operation without manual intervention.
Periodic testing of emergency lighting equipment is required for at least 30 seconds every 30 days plus for at least 90 minutes annually for battery-powered lighting.
Some units available can activate the test cycle with a hand-held remote controller, eliminating the need for a worker to carry and climb a ladder for access. And some manufacturers offer units with microprocessor controlled self-testing/self-diagnostics capability that automatically performs the 30-second tests at least every 30 days, with failure exhibited on a status indicator detectable by visual inspection. Usually, there is an LED read-out on the side of the fixture that tells of any problems, such as a spent lamp or a battery that is not taking a charge. This type of testing has the advantage that it samples constantly and can be connected to an audible alarm or PC-based monitoring system.
Decorative wall-mounted and ceiling mounted architectural emergency lights are becoming popular alternatives to the industrial-looking two-lamp bug eye fixtures.
Architecturally inspired styles abound, including wall sconces, low profile recessed high hats that are inconspicuous in commercial settings, and path lighting. Some manufacturers provide emergency lighting in the same decorative fixture lines as non-emergency fixtures, enabling consistency of appearance throughout a space.
For example, there are emergency battery back-up products that go inside T5 fluorescent fixtures. Available as a factory-installed option or as a field installation, the technology typically reduces the number of lamps, for example, powering only two lamps in a four lamp fixture or one lamp in a two lamp fixture as long as the reduced lighting provides enough illumination to provide the minimum required light level for 90 minutes. This capability in fluorescent fixtures eliminates the need for separate fixtures that would otherwise be necessary to provide the required minimum level of light for emergency lighting.
In areas where lighting is infrequently needed—for example, little-used staircases, storage areas, restrooms and corridors—there are energy-conserving fluorescent stairwell luminaires that can do double duty. Featuring motion sensors that activate or raise the level of illumination when occupancy is detected, these fixtures come with emergency back-up batteries which provide the required 90 minutes of illumination should there be a power failure.
New players in all sorts of lighting installations, LEDs are also making inroads into emergency exit signs. They consume very little power and last an extraordinarily long time compared to alternative light sources. LED fixtures are especially suitable for illumination of stairwells, step landings, wheelchair ramps and exit corridors—locations where changing the lamps can be cumbersome or disruptive. Units that offer user-selectable intensity control (e.g. multiple levels of intensity) allow the lighting to satisfy architectural as well as code requirements.
There are also emergency lighting units available designed to withstand abuse in vandal prone areas. These fixtures are often made of high impact polycarbonate and may feature tamperproof housings. Those with waterproof gaskets are suitable for outdoor use.
By William & Patti Feldman