Emergency lighting fixtures are required to be installed in all commercial, industrial and other buildings with public access to help ensure the safety of a building's occupants when the normal lighting system fails. Emergency egress lighting systems (commonly known as exit signs) must illuminate the pathway floors leading to exits, including all passageways, corridor intersections, turns, stair treads and landings, exit doors, and the exit discharge, such that no point in the egress pathway is more than 100 feet from the nearest visible exit sign. Emergency lighting systems and exit signs should provide fully automatic operation and must operate for no less than 90 minutes during power interruptions.