Approach/Protection Boundaries

An arc flash boundary is the calculated distance from an exposed live part at which an unprotected worker is likely to receive a second-degree burn in the event of an arc flash. Both qualified and unqualified workers may cross the arc flash boundary as long as they are wearing appropriate arc flash PPE, as specified in NFPA 70E. Unqualified persons must be escorted by a qualified person to cross this boundary.

Keep in mind shock hazards and arc flash hazards are not the same thing. The limited approach boundary is the distance from an exposed live part at which a shock hazard exists. Both qualified and unqualified workers may cross the limited approach boundary as long as they are wearing appropriate shock hazard PPE, as specified in NFPA 70E. Unqualified persons must be escorted by a qualified person to cross this boundary.

The restricted approach boundary is the distance from an exposed live part at which there is an increased risk of shock from arc-over or inadvertent movement. Unqualified workers may not cross this boundary. Qualified workers must wear PPE appropriate to the voltage they are exposed to, as specified in NFPA 70E. At a minimum some form of documentation is required to cross this boundary, often an approved work permit is required.