Which statement about arc flash boundaries is true?

• A. The arc flash boundary is the same for all voltages.
• B. The boundary is determined only by the installation location.
• C. The boundary is defined by the incident energy and PPE category, and it varies with voltage.
• D. The boundary is only relevant for de-energized equipment.

Answer: (C)

Arc flash boundaries define how far from energized equipment an arc flash hazard could reach and cause harm. The key point is that this boundary isn’t a fixed distance; it’s defined by the incident energy at a given location, which in turn determines the PPE category needed to protect the worker. Because incident energy depends on voltage (and factors like fault current and clearing time), the boundary changes with voltage.

This matters because knowing the boundary tells you what PPE is required and how far you must stay away when working with energized equipment. It’s not determined by where the equipment is installed—it's about the electrical conditions and potential energy during a fault. It’s also relevant for energized, not just de-energized, situations.

Why the other statements don’t fit: the boundary isn’t the same for all voltages; it isn’t determined solely by installation location; and it isn’t only relevant for de-energized equipment.