In 1956, the NEC^® required emergency illumination to be “designed and installed that the failure of any individual lighting element, such as the burning out of a light bulb, cannot leave any space in total darkness”. Over time, that language evolved into “emergency lighting systems shall be designed and installed so that the failure of any illumination source cannot leave in total darkness any space that requires emergency illumination.

From the 1956 code language, it’s clear that the original idea was to address the short life of a common incandescent light bulb. Newer technology has brought fluorescent emergency luminaires with ballasts and LED luminaires powered by drivers into the spotlight and with it come many questions for the designer, installer, and inspector:

• What is an “individual lighting element”?
• Is an LED driver a lighting element?
• Is a ballast a lighting element?
• If the failure of “any individual lighting element” shall not leave an area in darkness, then does each LED emergency luminaire require two drivers?
• Is an emergency luminaire with one driver supplying two arrays of 16 LED lamps each code compliant or are two fixtures required to serve the area requiring emergency illumination?
• Are the many LED lamps on an array of lamps tied to the others in series? If a single LED lamp in an array fails will the others in the same string still work?
• Is an emergency luminaire with one ballast supplying two fluorescent lamps code compliant or are two light fixtures required to serve the area requiring emergency illumination?

The current NEC^® code language is a step closer but still doesn’t answer all of the questions. In the 2020 NEC^®, the phrase “individual lighting element” was replaced with “illumination source” and the example of “such as the burning out of a lamp” was removed so as not to narrow down the possibilities of what an “illumination source” may apply to.

It is likely that this code section will see further revisions in the future.

Become familiar with the above concept and what the code is trying to accomplish. There can be a huge delay if during the final inspection, the inspector finds several areas of the building where the failure of an individual lighting source such as the burning out of an emergency luminaire lamp can result in the area requiring the illumination to be left in total darkness.

Below is a preview of the NEC^® (NFPA 70). See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the edition of the NEC^® being enforced.

NEC 700.16 Emergency Illumination.

(A) General. Emergency illumination shall include means of egress lighting, illuminated exit signs, and all other luminaires specified as necessary to provide required illumination.

(B) System Reliability. Emergency lighting systems shall be designed and installed so that the failure of any illumination source cannot leave in total darkness any space that requires emergency illumination...

(C) Discharge Lighting. Where high-intensity discharge lighting such as high- and low-pressure sodium, mercury vapor, and metal halide is used as the sole source of normal illumination, the emergency lighting system shall be required to operate until normal illumination has been restored.

(D) Disconnecting Means. Where an emergency system is installed, emergency illumination shall be provided in the area of the disconnecting means required by 225.31 and 230.70, as applicable, where the disconnecting means are installed indoors.

Exception: Alternative means that ensure that the emergency lighting illumination level is maintained shall be permitted.