What are boundary distances in the context of arc flash?

• A. The restricted and limited approach boundaries define how close a worker may approach energized parts with appropriate PPE; arc flash boundary defines where incident energy is 1.2 cal/cm^2
• B. They indicate only weather boundaries
• C. They relate to color coding
• D. They are not PPE-related

Answer: (A)

Boundary distances around energized equipment are about keeping workers safe from arc flash and electrical shock by defining how close someone may approach and what protective gear is required. There are two sets of boundaries that work together. The restricted approach boundary is the closest safe distance to exposed energized parts for someone who is trained and wearing the proper PPE; crossing it means additional precautions and supervision. The limited approach boundary sits a bit farther out and applies to tasks where there’s a risk of contacting energized parts, requiring a higher level of PPE and safety controls. The arc flash boundary is a separate line that marks where the potential incident energy could reach 1.2 cal/cm^2 or more; inside this boundary, the energy level is sufficient to cause a second-degree burn to bare skin, so arc-rated PPE and protective measures are required. Distances depend on the system’s voltage, available fault current, and how quickly the fault would be cleared, and they’re determined through analysis or NFPA 70E tables. This option correctly ties the boundary concepts to PPE requirements and the 1.2 cal/cm^2 threshold, unlike the other choices that refer to weather, color coding, or non-PPE aspects.