What is the principle of de-energize-before-service and under what conditions is energized work allowed?

• A. Energize first
• B. De-energize and isolate equipment; if energized work is unavoidable, conduct a documented energized work procedure with risk assessment, engineering controls, and appropriate PPE
• C. Work without energy isolation
• D. Remove PPE before service

Answer: (B)

The principle at work is to remove the energy source and isolate equipment before performing service to protect workers from shock, burns, and arc flash. This is typically done with a lockout/tagout process so that no energy can re-energize the equipment while work is happening.

Energized work is allowed only when de-energizing is not feasible. In that case, a documented energized work procedure must be followed. This includes a formal risk assessment, engineering controls to minimize exposure (such as barriers, guards, insulation, or remote operation), administrative controls (permits, job steps, supervision), and the use of appropriate PPE (arc-rated clothing, face protection, insulated gloves, etc.). The work should be planned, authorized, and monitored, with steps to re-establish a safe condition if the situation changes.

Choosing to energize first would unnecessarily expose workers to electrical hazards; working without energy isolation defeats the safety purpose of the control; and removing PPE during work would remove essential protection.