Abstract: At 11:15 a.m. on December 19, 2019, two employees were replacing fluorescent lighting ballasts in the conference room's overhead lighting system. The circuit breaker labeled "Lighting" (circuit #3 in panel H-B) was opened, and Employee #1 used a Fluke Model 324 meter to verify that the power supply wire feeding one of the fluorescent ballasts in the lighting fixtures was deenergized. He did not verify that the other power supply wires present in the fixtures were deenergized, or that the neutral wire did not have any voltage or current present. Employee #1 began removing the fluorescent ballast from the fixture by cutting the power supply wire and stripping the insulation from the wire to insert it into a wire connector. He then cut the neutral wire from the ballast and, while attempting to strip the insulation from the conductor still connected to the wiring system, he received an electric shock which caused his body to "torque," causing him to lose his balance and fall approximately 5 feet from the portable A frame ladder he was standing on to the floor surface of the conference room. Employee #1 suffered a fractured humerus in his left arm and was hospitalized. CalOSHA identified several causal factors, including but not limited to: -The employee (authorized person) failed to lock the disconnecting means in the "open" position on all electrical branch circuits providing power to a 277v lightning system with a shared neutral conductor. -The employee did not properly test the conductors in the light fixture that he was working on to verify that no voltage was present. -The employer failed to identify and correct the hazardous condition of employees performing work on electrical systems with shared neutral conductors. -The employees had not received training on identifying and deenergizing electrical systems which utilize multiple line voltage conductors sharing a common neutral conductor.