Picture this: It’s a dark and gloomy morning outside; building occupants are going about daily work routines inside. As the day progresses, snow begins to fly; by mid-afternoon, everything is covered in a blanket of white. Under the weight of the freshly fallen snow, a power line goes down. Suddenly, the lights go out and building tenants are left in a sea of darkness. What happens next? Undoubtedly, there are people in the stairwells, the corridors, the elevators, the restrooms … do they panic? If your building is an elementary school, can children and teachers see to exit safely? If it’s a corporate office, can employees make out a path of egress?
Although power outages don’t occur that often, it’s essential that when they do happen, your building is properly equipped and can light a path to safety for the people inside. There are many different emergency lighting options for facilities; choices range from simple wall-mounted units to complex systems integrated into your building’s primary lighting system. Learn about some of your options:
Battery-Powered Unit Equipment
What they are: Compact battery-powered emergency lights, available in a variety of models (some are even equipped with exit signs). These emergency units are separate from primary lighting systems, and often have built-in test equipment or procedures that regularly exercise the fixture to ensure proper operation.
How they work: Attached to the wall or ceiling wherever lighting is needed in an emergency, these small units each have their own individual battery packs that provide approximately 90-plus minutes of power to small incandescent or halogen lamp heads when the overhead lights go out.
Keep in mind: These relatively inexpensive units offer instant start-up, which is crucial in an emergency situation – but, the batteries only last for a short length of time before they need to recharge. The UL Listing report indicates the specific batteries that must be used with these units; if you substitute a different battery, it may cause premature failure and/or damage to the equipment. These systems must also undergo periodic maintenance and upkeep, but built-in test options available on many models make this easier to manage and eliminate the need for manual testing: Failure to successfully complete a test exercise will activate a warning light to let you know that the unit needs service. Because the lights on these units are intrusive and very obvious, they may not be the ideal option in some cases due to design constraints. The possibility of vandalism in unobserved areas is also an increased risk with unit equipment because the heads are easily visible. Battery-powered unit equipment is sometimes used in conjunction with inverters or generators (see Diesel-, Gasoline-, or LP-Powered Generators and Inverters) to provide appropriate light levels to areas in a building that may not be as heavily populated.
Fluorescent Emergency Ballasts (FEBs)
What they are: Ballasts that work in conjunction with existing lighting systems to convert standard fluorescent fixtures into emergency lights.
How they work: When normal AC power supply fails, FEBs sense the power failure, immediately switch to emergency mode, and use batteries to illuminate lamps at a reduced lumen output. When AC power is restored, emergency ballasts return to charging mode until the next power failure. Ballasts can be mounted within or on top of lighting fixtures, or in remote locations.
Keep in mind: Because they use the existing lighting system to provide emergency lighting, no extra fixtures are needed. However, FEBs run on batteries – they are limited to 90 minutes of operating time, and will then need to recharge. Although a relatively low-cost option, one misconception about these systems is that they operate at full lumen output (providing the same amount of light offered in a normal lighting situation). These systems actually light only one, two, or three lamps in the fixture, and do so at a reduced lumen output: So, lighting levels are not as high as they would be normally. Because FEBs are battery-operated, they need to be tested to make sure batteries are functioning properly. As with battery-powered unit equipment, these systems are sometimes used in conjunction with inverters or generators (see Diesel-, Gasoline-, or LP-Powered Generators and Inverters) to provide appropriate light levels to areas in a building that may not be as heavily populated.
Diesel-, Gasoline-, or LP-Powered Generators
What they are: Generators that provide back-up emergency power to existing lighting systems, as well as to a variety of other building systems (HVAC, vertical transportation, etc.).
How they work: Selected fixtures are tied through a transfer switch to the generator in order to provide emergency lighting.
Keep in mind: Generators obviously last longer than battery-powered options – essential in healthcare applications and other types of facilities where certain procedures must continue during a power outage. But, generators can be a nuisance when it comes to maintenance. Fuel has to be stored properly and changed out periodically; the system must be insulated and protected from outdoor elements; and generators should be tested at least once a month, according to Doug Andrews, general manager, Chloride Systems/Div. Genlyte Group, Burgaw, NC. “If you have other equipment that you need to provide emergency power to – above and beyond just your lighting – you’re probably locked into [using] a generator: But, [you have to be] willing to devote your resources to a device that requires significant maintenance. If you don’t, it’s like anything else … when you really need it, it may not work.” Generators also have a lag time (sometimes as great as 15 seconds) before necessary power can be provided to building systems. Fifteen seconds may not seem like much time, but to building occupants who are disoriented and confused, it may cause unnecessary panic. This lag time can also cause problems for HID lamps, which take several minutes to cool down before arc restrike can be initiated and the lamps can again offer light. However, newer lamps and devices are shortening the switching time, allowing generators to offer some of the benefits of a battery-powered system.
What they are: Inverters are essentially UPS (uninterruptible power supply) systems. Providing convenient power for many styles of lighting, inverters turn existing lighting systems into emergency lighting systems. Inverters also provide a single-point source of power for all emergency lighting and exit signage, offering simple maintenance and a controlled, logical wiring scheme.
How they work: Inverters use large banks of batteries and sophisticated electronics to convert DC battery power to AC power, which is then supplied to a lamp through a transformer. Available in single- and three-phase models, inverter systems have different transfer time ratings to handle all types of lamps and applications.
Keep in mind: There is no interruption in power when using inverters, so they’re helpful for spaces with HID lamps, which cannot accept an interruption in power and still continue to function. The lighting levels provided by an inverter are also weaker than what they would be in a normal lighting situation. Inverters sometimes serve as an “instant-on” back-up solution while diesel-, gas-, or LP-powered generators are gearing up to provide longer-term power to emergency lighting. The equipment itself also takes up a large amount of space, and is also a more expensive option than some of the other choices available for powering lights in an emergency. “You have a large battery bank built in a cabinet that creates line voltage. When power fails, the inverter kicks on immediately; but there is a cost associated with that because of the size of the system,” explains John Levesque, national sales manager, The Bodine Co., Collierville, TN.
The choices you make about your facilities’ emergency lighting systems must meet (or exceed) regulations set by national, state, and local building codes (including the National Electrical Code®, the National Fire Protection Association’s Life Safety Code®, and the Underwriters Laboratories standards). But most professionals in the emergency lighting industry agree that carrying out solely what code requires may not be good enough. “Code itself applied in real life is a bare, bare minimum in regards to emergency lighting,” emphasizes Chloride Systems’ Andrews. “[Power outages don’t] happen often, but when [they do] happen, and if there’s an injury, it always winds up being an ugly event. If possible, provide a very good system that is above and beyond what the code requires.”
The Bodine Co.’s Levesque agrees: “Everyone’s safety is involved in getting out and away from the building. [Follow and meet] the codes, and [do] what is acceptable, but not always at just the minimum level.”
When selecting an emergency lighting system, make sure you not only understand code requirements, but that you understand different product offerings and what they can (and cannot) do for your facility. “Oftentimes … someone will go for the cheapest product, and then they end up having to use a whole lot of the cheap product to at least achieve code, as opposed to going through the proper steps of using a better product, using fewer of them, and actually cutting the cost of the job by going that direction. There is a lack of understanding [about] the products available,” says Levesque. “There are smarter, better products in the marketplace that can cost-effectively meet the goals of a facility in terms of ease of testing and high illumination [levels].”
Andrews recommends that facilities professionals search for manufacturers providing point-by-point photometric evaluations – computerized simulations that present a reproduction of lighting levels in a specific space based upon a client’s product selection. He also suggests that facilities professionals research emergency lighting manufacturers before making a purchase to ensure the company will be available to service its products and provide alternatives for replacement in the future. “Sometimes, [facilities professionals go with] the cheapest alternative, which tends to be just planting thousands of little [battery-powered] emergency units everywhere. That will meet code, but in the long run, the maintenance cost of that type of project will be much greater and provide much less illumination than using central systems or using good, high-quality, high-performance products,” says Andrews. “Looking solely at the unit cost of [an] emergency lighting product does not even remotely define the total installation cost or the ongoing maintenance cost.”
Energy efficiency is another significant consideration in emergency lighting. “Although energy codes regulate the amount of primary lighting that is allowed in buildings, these codes specifically exempt emergency lighting. It is good engineering and design practice to use the most efficient light sources. This not only ensures energy efficiency, but also maximizes battery life or minimal power draw on a generator,” says Jim Yorgey, technical applications manager at Coopersburg, PA-based Lutron Electronics Co. Inc. Donna Bard, product manager at Aurora, OH-based Technical Consumer Products Inc., agrees: “Energy efficiency is so important. [Energy-efficient products are available] that look good, that last a long time, and need minimal maintenance.”
Energy efficiency in emergency lighting will continue to improve in the future: More light from less power is what lies ahead. Yorgey indicates that there has been a higher demand for quality emergency lighting systems due to recent natural and manmade disasters. “This is leading to better and lower-cost solutions for emergency lighting requirements,” he explains. “Developments in battery and fuel cell systems [will provide] improved operating times and [life-cycles for] these systems.”
Now, think back to the scene you read about at the top of the page: What happens next? The answer depends on your emergency lighting system.
Leah B. Garris (firstname.lastname@example.org) is associate editor at Buildings magazine.
NFPA Life Safety Code 5-9.2.1 says: Emergency illumination shall be provided for a period of 1.5 hours in the event of a failure of normal lighting.
NFPA Life Safety Code 5-9.2.1 means: Your emergency lighting needs to last for at least 90 minutes when the power goes out.
NFPA Life Safety Code 5-9.2.1 says: Emergency lighting shall be arranged to provide initial illumination that is no less than an average of 1 footcandle and a minimum at any point of 0.1 footcandle measured along the path of egress at floor level. Illumination levels may decline to 0.6 footcandle average and a minimum at any point of 0.06 footcandle at the end of emergency lighting time duration. A maximum to minimum illumination uniformity ratio of 40 to 1 shall not be exceeded.
NFPA Life Safety Code 5-9.2.1 means: Emergency lighting levels should maintain an average of 1 footcandle (the average lighting level in an office space ranges between 15 and 35 footcandles); but, that number can drop to 0.6 footcandle as 90 minutes draws closer. There shouldn’t be bright spots of light followed by spots of darkness – emergency lighting levels should be fairly even.
NFPA Life Safety Code 31-1.3.7 says: A functional test shall be conducted on every required emergency lighting system at 30-day intervals for a minimum of 30 seconds. An annual test shall be conducted for the 1.5-hour duration of the test. Written records of visual inspections and tests shall be kept by the owner for inspection.
NFPA Life Safety Code 31-1.3.7 means: On systems without self-diagnostic/self-testing mechanisms, emergency lighting needs to be tested every 30 days for at least 30 seconds; it also needs to be tested once per year for 90 minutes. The results of these tests need to be documented in case of fire inspections.
NFPA Life Safety Code 5-8.1.4 says: Illumination shall be so arranged that the failure of a single lighting unit will not leave any area in darkness.
NFPA Life Safety Code 5-8.1.4 means: If one emergency lamp goes out, building occupants should still be able to track the path of egress.
NFPA Life Safety Code 8-8.1.3 says: The floors of means of egress shall be illuminated at all points, including angles and intersections of corridors and passageways, stairways, landings of stairs, and exit doors to values of not less than 1 footcandle measured at the floor.
NFPA Life Safety Code 8-8.1.3 means: The path that occupants follow to exit the building should be illuminated appropriately, with changes in direction, stairs, and doors clearly visible.