Both NFPA 101 Life Safety Code and the IBC require a specific amount of foot-candle illumination at the walking surface from the emergency lighting system.

A lighting designer considers a great many things when specifying emergency luminaires for a project including the illumination output levels, mounting height above the walking surface, and luminaire spacing to ensure illumination uniformity.

The design engineer may have gone to great lengths to ensure proper illumination levels when putting the plans together.

Detouring from the plans by installing the luminaires higher above floor than specified, or using a different luminaire with lower lumens, or using less luminaires to save money, or even spacing the luminaires too far apart are all things that will have a negative effect on the final performance of the emergency lighting system.

It’s always a good idea to run any field changes by the electrical designer for approval.

One thing the electrical inspector will be looking for during final inspection is the height above floor of all installed emergency luminaires. If any emergency luminaires seem to be mounted excessively high, their illumination level at the walking surface might be insufficient to meet the minimum requirements for safe egress.