Best practices for emergency lighting

Explore how to implement safe, code-compliant, and cost-effective emergency lighting systems.

03/29/2018


This article has been peer-reviewed.Learning Objectives:

  • Understand code requirements for emergency lighting.

  • Learn about various approaches to emergency lighting design.

  • Review best practices in laying out and selecting light fixtures.


Emergency illumination is defined as the emergency lighting within a building that is in place to light the path of emergency egress when the normal supply of power is not available, and it is a key component to the life safety system. Numerous codes outline the rigorous path to achieving a code-compliant and safe emergency illumination system. It’s vital to understand emergency lighting and how to implement emergency lighting systems that are code-compliant, safe, functional, and user-friendly.

IBC requirements

Figure 1: The most common type of emergency illumination, sometimes referred to as “bug-eyes”, includes an internal battery and can be connected to the local emergency branch circuit. All graphics courtesy: RTM Engineering ConsultantsThe 2015 International Building Code (IBC) specifically requires the path of egress be illuminated at all times the room or space is occupied. The IBC maintains that the illumination levels in the path of egress must not drop below 1 fc under normal power conditions. This is not an average threshold, but an absolute minimum under normal power conditions. When laying out emergency egress lighting, the path must be closely analyzed using photometric software to ensure no point along the path of egress is less than 1 fc. On the other hand, the IBC maintains different standards for lighting under emergency power. Lighting provided under emergency power, when normal power is lost, is allowed to maintain an average of 1 fc and a minimum of 0.1 fc measured along the path of egress along the floor. Lighting levels are permitted to decrease throughout the specified time duration to an average of 0.6 fc and a minimum of 0.06 fc at the end of the required emergency lighting duration. The maximum-to-minimum lighting uniformity ratio shall not exceed 40:1.

The IBC defines any room that is required to have two or more exits as a space that must have properly illuminated aisles, corridors, stairways, and ramps. After defining how a room must be properly illuminated, the IBC goes on to describe how a building as a whole must be illuminated. In buildings that require two or more means of egress, all interior stairs, interior ramps, exterior stairs, exterior ramps, exit passageways, vestibules, and exterior landings must be automatically illuminated. The utility rooms in any type of building also must be illuminated, such as electrical equipment rooms, fire command centers, fire pump rooms, generator rooms, and public restrooms with an area of greater than 300 sq ft.

The IBC defines the amount of time required for emergency illumination at 90 minutes, whether the back-up power source is a centralized storage battery system, local unit equipment, or an onsite generator.

NFPA 101 requirements

Figure 2: This diagram depicts an emergency illumination system within a commercial office building where the dual-head emergency units needed to be spaced out.NFPA 101: Life Safety Code, 2018 edition, details the illumination requirements for means of egress. Starting out, the NFPA outlines that illumination shall be continuous during the time in which the conditions of occupancy require that the means of egress be available for use. The code goes on to state that artificial lighting shall be employed at such locations and for such periods of time as are necessary to maintain the illumination to the minimum criteria values.

As defined in NFPA 101, for emergency systems, lighting shall be arranged to provide initial illumination that is not less than an average of 1.0 fc and at any point not less than 0.1 fc, measured along the path of egress at floor level. Illumination levels shall be permitted to decline to not less than an average of 0.6 fc at the end of the required 90-minute period. Similar to the IBC, maximum-to-minimum illumination shall not exceed a ratio of 40:1.

Figure 3: This diagram depicts an emergency illumination system within a commercial office building where a required amount of the LED light fixtures already chosen for the space were connected to an emergency lighting UPS.In regard to automatic lighting controls, NFPA 101 describes how and when it is permissible to control emergency egress lighting. The following criteria must be considered when specifying lighting control devices.

  • Lighting control devices must be equipped to turn on emergency egress lights upon the loss of normal power.

  • As required for new buildings, lighting control devices must be activated by the building fire alarm system, if a fire alarm panel is provided.

  • As photoluminescent signage becomes more prevalent in building design, the lighting control device must not turn off any lighting that photoluminescent signage relies on.

  • Lighting control devices also must not turn off any lights that are battery-powered.

  • As a whole, when using energy-saving nodes, time clocks, and sensors, the designer must ensure that these devices do not compromise the continuity of the emergency lighting system.

  • Time clocks and lighting control panels must be carefully specified so that circuits do not get stuck in the “off” or open position, as this type of equipment should be specified so that the absence of power creates a fail-safe “on” or closed condition for controls.


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