The Building and Life Safety Codes specify where exit signs and emergency lighting must be installed, how much illumination is needed, how long emergency luminaires must stay on after an outage, and how they must perform. The NEC^® provides the rules on how emergency lighting must be configured. There is however one requirement in the NEC^® (often overlooked by the electrician) which specifies a location where emergency lighting must be installed.

NEC 700.16(D) requires the following: 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.

The Building and Life Safety Codes dictate where an emergency system is required to be installed. These rules are based on occupancy type, number or required exits based on occupant load, and common path of egress travel distance to the exit discharge. The larger and more complex a building is, the harder it is to make it to the exit discharge and then to a public way during an emergency.

A small business space (Group B occupancy) with a tiny occupant load, such as an insurance company in a strip mall, with a single entrance/exit, is not required by the IBC to have emergency lighting or exit signs since those that enter will easily be able to find their way out in an emergency. Alternatively, a large assembly occupancy (Group A) such as a theatre or night club will be required by the IBC to have multiple exits leading to a public way. Because of the complexity of the many exit paths, emergency lighting and directional exit signs are required to ensure occupants can easily find their way to the exit discharge when the power goes out.

If an emergency system is required and installed, the NEC^® will require emergency illumination in any interior area where there is a disconnecting means required by 225.31 (feeder or branch circuit disconnect) and 230.70 (service disconnect).

• Section 225.31 requires a disconnecting means for all ungrounded conductors that supply or pass through the building or structure.
• The disconnecting means required in 230.70 is a service disconnect.

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. Control devices in the emergency lighting system shall be listed for use in emergency systems. Listed unit equipment in accordance with 700.12(I) shall be considered as meeting the provisions of this section.

(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.