Abstract: On January 28, 2013, Employee #1, with Red Hawk Fire & Security (Ca) LLC, was replacing an old fire alarm system with a new one in a 14 story building, with a coworker. Employee #1 and the coworker were searching the basement level to find a junction box containing wires to the system. Employee #1 looked at the schematics, and it appeared that the juncture box was in the fan room where Employee #1 located an unmarked junction box which was the same color and dimensions that held the wires on the other floors. This box (18 in. by 18 in.), however, turned out to be 480 volts. The coworker loosened four screws in the corners and was holding the screwdriver when he began to lift and to pull the cover away from the box. While doing this, the coworker tilted the cover and touched it inside the box. When the coworker did this, an arc flashed that threw both Employee #1 and the coworker back. Employee #1 sustained burn injuries to his face and hands. Employee #1 later learned there was no junction box holding the missing wires. The wires had been spliced and dropped in one of the pipes. Employee #1 instructed his coworker to open an unmarked box that should have been marked with voltage, amps and other identifying information. The coworker did not have electrical training. The coworker was a full-time permanent employee of the employer with no other contracts. Employee #1 was hospitalized.