What boundary is referred to as the 'Just Curable Burn' distance? What is the cal/cm2 rating?

• A. The Restricted Approach Boundary, 5 cal/cm2
• B. The Limited Approach Boundary, 1 cal/cm2
• C. The Flash Protection Boundary is referred to as the "just curable burn" distance, 1.2 cal/cm2
• D. The Prohibited Boundary, 100 cal/cm2

Answer: (C)

In arc flash safety, boundaries are defined by the amount of incident energy (in cal/cm2) a person could be exposed to from an arc. The distance described as the “just curable burn” corresponds to the Flash Protection Boundary. It marks the point where the incident energy reaches about 1.2 cal/cm2, the level at which a burn could occur on unprotected skin. Therefore, within this boundary, proper arc-rated PPE is required to protect against that energy level. The other boundaries relate to different approach distances and different energy thresholds, so they are not the “just curable burn” distance.