Which factor is used to determine the AFB in arc flash PPE category method?

• A. The working distance
• B. The conductor color
• C. The ambient temperature
• D. The ground resistance

Answer: (A)

Arc Flash Boundary is the distance from the arc source at which the incident energy reaches a defined threshold (1.2 cal/cm^2). In the PPE category method, this boundary is determined using the working distance—the distance you expect to be from the source while performing work. Incident energy drops as you move farther from the arc, so selecting a working distance allows you to look up or calculate the energy at that distance and thus locate the boundary where that energy equals the threshold. The other factors listed don’t set this boundary: conductor color, ambient temperature, and ground resistance don’t define the energy-distance relationship used to establish the arc flash boundary.