The National Electrical Code (NEC) requires emergency lighting systems to be installed in buildings and other structures for the purpose of providing illumination during power outages. Specifically, NEC 700.12 states that all exits, accesses to exits, aisles and passageways must have emergency lighting with at least 0.1 footcandles of light at floor level on the path of egress. In addition, NEC 700.27 specifies that these lights need to meet certain reliability requirements such as battery back-up power sources and self-testing capabilities so they can continue to provide illumination even if there is a power outage or interruption in service.