Abstract: A supervisory electrician and his apprentice had just installed new conduit leading to a carbon dioxide tank. The supervisor and a building engineer thought they had deenergized the circuit by opening a circuit breaker. However, the labeling was in pencil; and they had opened and tagged only one of the two circuit breakers protecting the carbon dioxide unit. (A 15-ampere circuit breaker was opened, but a 50-ampere circuit breaker was never located.) The supervisor hooked a metal fish tape that was in the conduit to 480-volt, three-phase No. 8 conductors that were still energized. When the fish tape contacted the conductors, the supervisor was electrocuted. His employer had instituted a rule requiring employees to check wiring for voltage to assure that circuits are deenergized. The supervisor had apparently failed to follow this rule.