Which boundary requires use of shock protection techniques due to proximity to a shock hazard?

The boundary that requires the use of shock protection techniques due to its proximity to a shock hazard is the restricted approach boundary. This boundary is defined in electrical safety standards to indicate an area where a person must take specific precautions to avoid exposure to shock hazards.

When working near energized parts, the restricted approach boundary is set to ensure that individuals maintain a safe distance from potential electrical hazards where severe injury could occur. This boundary requires individuals to wear appropriate personal protective equipment (PPE) and to follow established safety protocols to mitigate the risk of electrical shock.

Understanding the context of other boundaries helps clarify why the restricted approach boundary is the correct choice. The prohibited approach boundary indicates areas where no unqualified personnel are allowed to enter without specific safety measures, and thus, it's even more restrictive than the restricted approach boundary. The limited approach boundary is a less critical area than the restricted boundary and does not necessarily require the same level of protection. Safe distance boundary denotes a general area which is assumed to be free from shock hazards, thereby not necessitating specific shock protection techniques.