Prohibited Approach Boundary
The Prohibited Approach Boundary (PAB) is a legacy shock protection boundary defined in older NFPA 70E and CSA Z462 standards as the innermost distance from an exposed energized conductor where entering is considered equivalent to direct contact due to high risk of flashover or arcing. Current standards (NFPA 70E 2015+, CSA Z462) have eliminated PAB, as shock protection requirements are fully addressed at the limited and restricted approach boundaries, with PAB adding no additional requirements.
On a manufacturing shop floor, the PAB concept historically applied to work near panels, MCCs, VFDs, or switchgear. In modern practice, any task that would cross the old PAB is treated as energized contact work, requiring de-energization as the default per WorkSafeBC Part 19. If energized work is justified, only qualified persons may enter the restricted approach boundary (the functional equivalent of PAB) with voltage-rated gloves, insulated tools, and written procedures. Physical barricades and signage are set at the more conservative of arc flash or limited approach boundaries. Legacy labels still showing PAB should be interpreted as requiring full contact-equivalent controls.
Does WorkSafeBC explicitly define a Prohibited Approach Boundary in Part 19?
No. WorkSafeBC Part 19 defines minimum approach distances and limits of approach based on voltage, but does not use NFPA 70E terminology of limited/restricted/prohibited boundaries. For compliance, shock boundaries must be mapped from CSA Z462/NFPA 70E onto WorkSafeBC's mandated distances, treating the innermost space (former PAB) as equivalent to direct contact risk.
Is Prohibited Approach Boundary still in force under CSA Z462 or NFPA 70E?
No. Both CSA Z462 and NFPA 70E (2015 and later) removed the term. CSA Z462 states: 'The term prohibited approach boundary was deleted... as shock protection requirements apply only at the limited and restricted approach boundaries; the prohibited approach boundary did not trigger any additional requirements.' Legacy documents still describe PAB, but SafeDesk should flag it as legacy terminology.
How should an arc-flash label with PAB be interpreted in 2026?
Treat the PAB distance as the point where any approach is effectively direct contact work, requiring full justification and control. In modern practice, map PAB to the inner zone beyond the restricted approach boundary. SafeDesk should recommend updating labels to current CSA Z462/NFPA 70E conventions, removing PAB from new labels, and treating the distance as requiring energized work procedures or de-energization.