On Emergency Lighting, Part 1

The building codes used to determine the proper application of emergency lighting include International Building Code (IBC), NFPA 101: Life Safety Code, NFPA 70: National Electrical Code, NFPA 110: Standard for Emergency and Standby Power Systems, and NFPA 111: Standard on Stored Electrical Energy Emergency and Standby Power Systems. Be aware that your local jurisdiction may not be enforcing the most recent code or standard. Your locality may still be working on a previous version.

IBC Section 1006.1 requires that the means of egress must be illuminated at all times that the building space served by that means of egress is occupied. By definition, egress is a “continuous and unobstructed path of vertical and horizontal travel from any occupied portion of a building or structure to a public way. A means of egress consists of three separate and distinct components: the exit access, the exit, and the exit discharge.” Most local jurisdictions include after-hours cleaning crews in the consideration of a building as being occupied, so lighting controls for means of egress must function automatically.

NFPA 101: Life Safety Code provides clear expectations for the emergency lighting. The initial code source for determining the proper application of emergency lighting is located in NFPA 101 Chapter 7. Emergency illumination is required for buildings as stipulated in Chapters 11 through 43 of this code. Section clarifies that emergency lighting is only required for the purpose of exit access, which includes only designated stairs, aisles, corridors, ramps, and escalators to a defined public way. The parameters for emergency lighting as defined in NFPA 101 are the requirements for stairs to have a minimum of 10 fc (108 lux) measured at the walking surface, and a minimum of 1.0 fc (10.8 lux) for floors and walking surfaces. There is an exception for assembly hall occupancies of 0.2 fc (2.2 lux) during periods of performances or projections involving directed light, such as a movie theater. In the event of a power outage, the emergency lighting must activate within 10 seconds. Additionally, battery-powered emergency lighting must be continuously available for 90 minutes from the beginning of the power outage. The emergency illumination must be spaced to provide initial illumination along the defined path of egress of not less than an average of 1.0 fc (10.8 lux) and not less than 0.1 fc (1.1 lux) at the floor of the defined egress pathway. After 90 minutes, the illumination levels are permitted to decline along the path of egress as the emergency power source discharges to an average of 0.6 fc (6.5 lux) but not less than 0.06 fc (0.65 lux).

NFPA 101 Article 7.9.3 requires emergency lighting systems to have periodic functional tests. The functional testing is to be conducted monthly for a minimum of 30 seconds, with an annual test of 90 minutes required for battery-powered systems. There must be written documentation confirming the mandated monthly and annual functional testing, including visual inspections of the equipment. NFPA 101 also allows self-testing and self-diagnosis as long as the self-testing is compliant with the manual requirements. For emergency lighting systems where self-testing is performed by a computer-based system, a computer-generated report detailing the history of the tests is acceptable.

Exit signage is required by NFPA 101 Article 7.10. The exit signs cannot be spaced more than 100 feet apart and must be readily visible in all directions from the exit access. Exit signs with internal batteries are to be periodically tested in accordance with Article 7.9.3 and are to conform to UL 924. An exit sign’s illumination level is permitted to decline to 60% after 90 minutes of battery operation. Floor proximity egress path marking exit signs are required within 18 inches of the floor for various occupancies as detailed in NFPA 101 Chapters 11 through 43. The exit signs must comply with UL 1994: Luminous Egress Path Marking Systems and be approved for delineation of egress pathways. The system must operate continuously anytime the building fire alarm system is activated. The intent is to provide a clearly identifiable path of egress if the pathway is filled with stratified smoke and the only viable escape is very close to the floor.

Battery-powered emergency light sources must comply with NFPA 111. All of the battery-powered systems must comply with the UL 924 standard, which is consistent with NFPA codes and IBC. The most common battery-powered light source is a self-contained emergency lighting unit which incorporates the lamps, battery, and charger inside a single light fixture enclosure. These units are sometimes referred to as either “bug-eye” or “frog-eye” units within the construction trades. The units will usually contain a sealed, maintenance-free, lead acid battery. These lead-acid batteries have proven to be highly reliable and under most conditions will only need replacement at 7-year intervals. The units are powered from an unswitched circuit and will activate when the incoming voltage drops to 80% of nominal. Upon return of normal power, the units will remain on for a minimum of 15 minutes.

Functional testing of these units can be accomplished via multiple methods. They include an integral test switch, a remote infrared handheld device, or a factory-installed integral electronic device that automatically initiates code required tests. The automatic testing feature, if equipped, must produce an audible alarm with flashing LED if a test failure does occur. If the unit is not in alarm, and the device is UL listed for self-testing, then the testing requirement is satisfied and sufficient for the local jurisdiction. Witnessing the actual test is not required. The critical parameter for bug-eye placement is to maintain a minimum of 1.0 fc along the entire length and width of the designated pathway of egress.

Some emergency lighting units integrate exit signage and have sufficient battery power to also run remote lamp heads, which can be located adjacent to legally required exterior pathways to provide the required emergency illumination levels. Exit signs must comply with UL 924 for luminance and with the local jurisdiction for sign color and lettering size. The requirements for color and letter size do vary by locality. Illuminated exit signs internally house a source of illumination which can be LED, fluorescent, or incandescent lamps. Typically, the combination exit sign and emergency light source fixtures use sealed, maintenance-free, nickel-cadmium batteries. Exit signs are always unswitched and continuously illuminated. They will revert to their battery power when the incoming power drops below 80% of nominal voltage. All of the testing requirements for these are the same as for any other self-contained emergency lighting units. Incandescent and fluorescent lamped exit signs are required to have two lamps by code, in case one fails. The fluorescent lamps have an expected rated lamp life of 20,000 hours. The LED sources use less energy than the fluorescent lamps, and have an expected lamp life of 50,000 hours.

Another option for emergency lighting is to incorporate an emergency power unit into the linear fluorescent lighting fixtures. The emergency power unit is self-contained with a built-in battery, battery charger, and inverter. It can power a single fluorescent lamp within the linear fluorescent fixture continuously at a rated initial output of 1100 lumens. The emergency power unit must provide at least 60% of this lumen output after 90 minutes. The emergency power unit must be connected to an unswitched circuit which serves the area lighting fixtures. The unswitched circuit is permitted to run in a common conduit with the normal, switched, power circuit for the linear fluorescent fixtures. All of the periodic functional testing requirements as outlined in NFPA 101 must be accommodated by each emergency power unit. Since the emergency power units are self-contained, the units can be mounted remotely from the lighting fixture they serve. Typically, a remote mounted emergency power unit is capable of illuminating several lamps contained in multiple light fixtures.