What defines the arc flash boundary in terms of incident energy?

The arc flash boundary is defined as the distance from an arc flash source at which the incident energy becomes 1.2 cal/cm², which is considered the threshold for the onset of second-degree burns on human skin. This value serves as a critical safety measure in electrical work, allowing workers to assess risk and determine appropriate personal protective equipment (PPE) levels.

At this incident energy level, the chances of injury begin to rise significantly, making it essential for safety planning and hazard identification in electrical environments. Understanding this boundary enables workers to maintain a safe distance when working on or near energized equipment, thereby reducing the risk of severe injury from arc flash events. Thus, the value of 1.2 cal/cm² is foundational in electrical safety practices for establishing safe working areas and protocols.