Dual-lite dplaf50sg dpl exit sign, photoluminescent w/green lettersrs, aluminum frame, single face the dpl series of photoluminescent exit signage offers exit compliancewith ul listed legible viewing distances of 50′, 75′ and 100′. The signsabsorb and store ambient light from normal daylight, fluorescent,mercury vapor, metal halite, and led light sources, and are designedto provide emergency illumination for a minimum of 90 minutes in theevent of power loss. The signs require a continuous minimum of 5 footcandlesto maintain the charge. The dpl photo-luminescent exit signsdo not require ac or electrical power. All signs have a 25 year lifecycle.