Limited Approach Boundary:
An approach limit at a distance from an exposed live part within which a shock
hazard exists.
Restricted Approach Boundary:
An approach limit at a distance from an exposed live part within which there is
an increased risk of shock, due to electrical arc over and inadvertent
movement, for personnel working in close proximity to the live part.
Prohibited Approach Boundary:
An approach limit at a distance from an exposed live part within which work is
considered the same as making contact with the live part. NFPA 70E Annex C,
Limits of Approach describes the precautions that are required before crossing
each of these boundaries, and for some conditions establishes default distance
values.