The arc flash boundary is a critical concept in electrical safety that defines the distance from an energized electrical component or system within which a worker could be exposed to the thermal energy of an arc flash. It is determined based on the potential incident energy levels associated with an arc flash event.

The arc flash boundary is typically expressed as a distance in feet or meters. It represents the minimum safe distance at which personnel who are not properly protected with appropriate personal protective equipment (PPE) should stay away from the energized equipment. It serves as a safety zone to help prevent workers from being exposed to the thermal effects of an arc flash, such as intense heat, flames, and flying debris.