The keys to designing emergency lighting systems

There are numerous building codes in various editions in use around the country for engineers designing emergency illumination systems. The most widely used codes in effect today are NFPA 101: Life Safety Code and International Building Code.

03/20/2017


This article is peer-reviewed.

Learning objectives

  • Outline the codes and standards that define how to design emergency lighting systems.
  • Understand when and where emergency illumination is needed in commercial buildings.
  • Assess prices, testing, maintenance, and other variables when specifying emergency lighting systems.


Emergency lighting systems play a very important role in keeping buildings safe for public use. When in an unfamiliar place like a store, hotel, theater, or restaurant, sudden darkness presents a challenge for exiting a building. In darkness, attempts at finding an exit in an unfamiliar place could likely prove futile. If the building is a high-rise, imagine making the way down a stairwell in complete darkness. The situation can be especially worse where crowds have gathered, leading to unsafe panic conditions.

Figure 1: This is an example of a typical office-corridor lighting scheme using recessed fluorescent luminaires for emergency egress lighting. Emergency power is provided to three of the seven luminaires installed in the corridor. This lighting layout results in actual illuminance readings at the floor of 2.4 fc (25.9 lux) average, 6.7 fc (72.4 lux) maximum, with a minimum reading of 0.24 fc (2.59 lux). The emergency lighting provided in this corridor is sufficient to meet the requirement of the NFPA 101-2015: Life Safety Code. All graphics courtesy: Environmental Systems Design

For these reasons, emergency lighting systems must be carefully designed and properly constructed to provide a highly reliable system ready to illuminate the exit path when a power outage or other failure occurs. Fortunately, these systems are straightforward to design and simple to operate. While building codes, in regard to emergency lighting, are also fairly straightforward and easy to apply, proper specification is critical to optimal operations and reliability.

It’s all about the building codes

Usually, the code applicable to the design of the building—like the International Building Code (IBC), for example—sets the requirement to include an emergency lighting system as an element of the project design. The building code, alternatively, might invoke NFPA 101: Life Safety Code. NFPA 101 and IBC are written to coordinate with each other and define photometric performance. NFPA 70: National Electrical Code (NEC) defines installation requirements. In special building types, such as hospitals and health care facilities, occupancy-specific requirements may come into play. Always compare NPFA 101 with the applicable local building code as some have more stringent or different requirements.

Other codes referenced by NFPA 101 are likely applicable to the project as well. In particular, NFPA 110: Standard for Emergency and Standby Power Systems establishes performance and testing requirements for emergency and standby power systems including energy sources, converters, inverters, transfer switches, and controls. Similarly, NFPA 111: Standard on Stored Electrical Energy Emergency and Standby Power Systems does so for electrical stored-energy emergency power systems.

According to the IBC and NFPA 101, the following occupancy types require emergency lighting systems:

  • Ambulatory
  • Assembly
  • Commercial
  • Correctional
  • Day care
  • Educational
  • High-rise
  • Health care
  • Hotels and dormitories
  • Industrial
  • Lodging and rooming
  • Mercantile
  • Multifamily
  • Residential board and care
  • Storage
  • Underground and limited-access structures.

Figure 2: An illuminance calculation shows a stairwell. Illuminance values are shown in footcandles for the occupied condition. The where, how, and when of emergency lighting codes

Where: The basic requirement is to provide emergency lighting systems in all exit paths including stairwells, aisles, corridors, ramps, elevators, escalators, and passageways leading to an exit and to the public way. Code writers did leave some discretion to designers in regard to where emergency lighting is required. The 2015 edition of the IBC doesn’t explicitly say to provide emergency lighting in mechanical rooms or open-office areas, but these areas should be provided with emergency lighting systems.

A good practice is for designers to imagine themselves in an unfamiliar mechanical room, open-office area, or any other area of a building. Would lighting be required to make a safe exit? It is possible that power is lost only to lighting feeders leaving mechanical and electrical equipment still in operation? Exiting an unfamiliar mechanical or electrical room could be dangerous in these conditions.

For similar reasons, emergency lighting should be included in open-office areas. There should be adequate emergency lighting to light the path from the desk areas to the corridors. Similarly, don’t forget about exterior emergency lighting. The code requires emergency lighting in the exit path to the public way. Exterior lighting is very straightforward for an urban high-rise building located right on the property line. Consider what exterior lighting is required in a suburban setting, where the public way is remote from the structure. It’s best to clarify these situations with the authority having jurisdiction (AHJ) during the early stages of the project.

How: For most commercial building projects, NFPA 101 requires emergency lighting systems to use artificial lighting when emergency lighting is required. Natural daylighting cannot be relied upon for life safety applications. NFPA 101 does allow some industrial applications to use natural lighting, provided emergency lighting is required only during daylight hours.

When: Emergency lighting systems must be operable whenever the conditions of occupancy require means of egress to be available. It is possible to shut off emergency lighting systems when a structure is not in use; however, most emergency lighting systems are not provided with an off feature, resulting in higher reliability.


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