What defines the arc flash boundary?

• A. The distance from the arc source within which a second-degree burn could occur
• B. The distance within which a shock hazard exists
• C. The maximum allowed working distance
• D. The minimum clearance to prevent arc faults

Answer: (A)

The arc flash boundary is the distance from the arc source within which a person could receive a second‑degree burn if exposed to an arc flash. This boundary is defined using the incident energy level, typically around the threshold for a second‑degree burn (often cited near 1.2 cal/cm²). It serves as the practical limit for where arc‑rated PPE and specific safe‑work practices are required.

This boundary isn’t about electrical shock hazards, which have their own approach boundaries, nor is it a maximum working distance or a clearance to prevent arc faults. It specifically marks the zone where burn injury could occur, guiding protective equipment selection and safe procedures.