UL stands for Underwriters Laboratories, an independent product safety certification organization approved by OSHA to test products and issue certifications. UL 924 is the organization’s standard for the Safety of Emergency Lighting and Power Equipment. It governs the testing and certification of exit signs, emergency lights, and combo emergency exit signs to ensure these meet the standards specific to functionality, reliability, and visibility.  The UL 924 standards consider several other codes and documents, including NFPA 101: Life Safety Code, NEC 700 & 701, International Building Code (IBC), and International Fire Code (IFC).