Abstract: This invention relates to source of photoluminescence that attaches to a building structure, providing back-up lighting. A source of photoluminescence constructed in a accordance with the present invention consists of a base member which attaches to the building structure, a support member which releasably attaches to the base member, and photoluminescent material affixed to the support member so as to be visible to an occupant escaping from the building structure. The support member is formed with a cover member that in cooperation with the building structure hides the base member from view when the source of photoluminescence is attached to the building structure. The photoluminescent material is affixed to the outer surface of the cover member.