All commercial, industrial, public facilities and multi-unit residential buildings are required to maintain emergency lighting
to sufficiently illuminate internal and external means of egress. Paths of egress, including all passageways, turns, corridor intersections, stair treads and landings, exit doors, and additionally, the exit discharge, must be illuminated by egress lighting systems. Exit signs
are part of an emergency lighting system. These devices provide directional information to assist progression towards the emergency exit. Emergency lighting
is required to come on automatically within a few seconds in the event of a power outage and remain illuminated for the code-required 90 minutes so that a building can be quickly and safely evacuated.