Prohibited Approach Boundary (PAB)

Definition - What does Prohibited Approach Boundary (PAB) mean?

The prohibited approach boundary (PAB) is the distance away from a piece of energized electrical equipment. The distance of the boundary is determined by the amount of voltage running through the equipment.

For safety purposes, crossing a prohibited approach boundary is considered the same as making physical contact with a live part of the equipment due to the elevated risk level faced by workers within this boundary.

Safeopedia explains Prohibited Approach Boundary (PAB)

The prohibited approach boundary is the most high-risk of three approach boundaries used to delineate risk-level zones around electrical equipment. The two lower-risk approach boundaries are the restricted approach boundary and the limited approach boundary (lowest risk).

The PAB was developed by the National Fire Protection Association (NFPA) as part of its 70e standard governing electrical safety. It was eliminated by the NFPA in the 2015 edition of the 70e standard. The limited and restricted approach boundaries, as well as the arc flash boundary, remain in effect.

The PAB was eliminated because it did not trigger a mandatory action by employees. While the limited approach boundary marks the closest point at which an unqualified person can approach exposed energized equipment, and the restricted approach boundary marks the point at which workers must wear shock-protection equipment, the prohibited approach boundary did not mandate any new action be taken by workers. The boundary was thus eliminated in order to prevent confusion and to make the 70e standard easier to use and understand.

Despite being eliminated as a health and safety standard, the PAB may still be used within the context of electrical research or for documentary purposes.

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