UL 924 is the Standard for Safety of Emergency Lighting and Power Equipment. All luminaires are required by NEC^® 410.6 to be listed (certified by a nationally recognized testing laboratory such as UL) but not all luminaires used for emergency lighting are required to be listed specifically to UL 924.

Some luminaires might be listed to UL 1598 which is the Standard for Safety Luminaires, but they might also be equipped with an internal battery backup and relay that are certified to UL 924.

For luminaires certified to UL 924, part of the certification process is verifying that the luminaire provides the minimum illumination level at the walking surface required by the Life Safety Code and IBC 1008.3.5. These luminaires will come with installation instructions that dictate how far apart each luminaire can be placed and still maintain the minimum required illumination level at the walking surface.

According to UL 924 section SG3.2, the installation instructions for a luminaire tested at a mounting height of 7.17 feet or greater per SG2.2, shall specify the maximum mounting height based on the height of the lowest portion of the luminaire during the test of SG2.2.

In other words, unless the installation instructions specify otherwise, a luminaire certified to UL 924 cannot be mounted higher than 7.16 feet and still be expected to provide the minimum required illumination level at the walking surface. Always check the installation instructions before installing the emergency lighting fixtures. It gets real ugly at a final inspection when the inspector asks for installation instructions to verify that the emergency luminaires are installed no further apart and no higher than the installation instructions allow.

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 110.3(B) Installation and Use. Equipment that is listed, labeled, or both shall be installed and used in accordance with any instructions included in the listing or labeling.