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Emergency Lighting 101

By: Paul Markee
The use of emergency lighting in all commercial, industrial and institutional buildings has been mandated by national, state and local codes and standards since the 1940’s. In the event of an emergency, the emergency lighting systems must provide continuous illumination for a minimum of 90 minutes to allow the occupants to safely exit the building.

Emergency lighting systems must meet stringent criteria for construction and performance from UL’s Life Safety Equipment standard to the requirements of the National Electrical Code, Article 700, Emergency Systems and NFPA 101, Life Safety Code.

However, even though emergency lighting systems must meet these standards, not all systems are created equal. There are applications in which certain systems should not be used. The mounting height, light source and environment are very important to consider during installations. Some environmental issues to consider are temperature, dust, damp or wet location, and hazardous area.

The Life Safety Code requires an average of 1 foot-candle upon initial illumination of the emergency light, and an average of not less than 0.6 foot-candle after a 90 minute illumination period. Keeping that in mind, the proper choice of unit must me made to meet the foot-candle requirement. The light source of unit used in an office with a mounting height of 7 – 9 feet will not work in a situation where the emergency light is mounted 18 feet above the floor.

The majority of emergency lighting systems have SLC (Sealed Lead Calcium) maintenance-free batteries. These batteries generally have a 5 – 7 year life expectancy as long as it is maintained in an operating temperature range of 60 to 80° F. As the temperature increases above 80° F, the life of the battery decreases dramatically. When the temperature decreases, the battery life will increase, but the run-time of the battery will decrease, thus not allowing the system to maintain the required 90 minute illumination. The Sealed Nickel Cadmium maintenance-free battery is an alternate when it comes to temperature. These batteries offer a 12 – 15 year life with an operating range of –4 – 158° F.

There are also refillable Lead Acid and Nickel Cadmium batteries. These batteries require maintenance, but are great batteries to consider for temperature issues. The Lead Acid battery has an expected life of 8 – 12 years if maintained in an operating environment of 32 – 105° F. The Nickel Cadmium battery will have a life of 20 – 25 years, with an operating range of –22 – 140° F.

There are emergency lighting units that are specifically designed for dusty, damp and wet environments. An installer can not place any unit into these situations and expect them to function as designed. Standard metal emergency lighting units will allow moisture and dust into the enclosure. There have been situations where this has occurred and the result is a shorted printed circuit board because the moisture accumulated and dripped on the board components, or the dust from a metal grinding operation accumulated over time in the enclosure creating a connection between components.

Hazardous environment units are again designed for their particular applications. The NEC developed Classes, Divisions and Groups for these situations. Class I refers to areas where inflammable gases or vapors may be present in sufficient quantities to produce explosive or flammable mixture. Class II units are for areas where combustible dusts are present. Class III systems are for areas where ignitable fibers are present in sufficient quantities to produce ignitable mixtures. Division 1 indicates an area where the hazardous condition is normally present either continuously or periodically. Division 2 are areas where the hazardous condition is present due to accidental rupture, breakage or unusual faulty operation of a closed container or system. The Groups are broken down by particular categories based on the Class. Under Class I, Group A is for Acetylene, Group B for Hydrogen, Group C for Ether and Group D for Gasoline. Class II has Group E for Metal Dust, Group F for Coal Dust and Group G for Grain Dust.

As you can see from the above information, the application of emergency lighting systems is an important factor to consider when specifying, purchasing and installing such systems.

Call ExitSignage today at 866-697-9560 to discuss your emergency lighting needs.