This Aerospace Recommended Practice (ARP) provides criteria for design and location of power supplies, controls, light fixtures, and associated equipment which are used to provide emergency illumination in transport aircraft, designed to FAR 25 (Ref. 1) for operation under FAR 91 and FAR 121 (Ref. 2), and also in compliance with FAA Advisory Circular AC25.812-1A (Ref. 3). It is not the purpose of an ARP to specify design methods to be followed in the accomplishment of the stated objectives.