Which factor is NOT listed as a determinant of arc flash severity?

• A. Ambient temperature.
• B. Incident energy at location in the power system.
• C. Distance you are from the arcing event.
• D. Duration of arc event.

Answer: (A)

Arc flash severity is defined by the incident energy that could reach a person, which is governed by how much energy the arc delivers and how much exposure you have. The key factors that drive that energy are the electrical conditions creating the arc (such as voltage and the available fault current) and how you experience the arc in terms of distance and how long the arc lasts. The farther you are from the arc, the less energy you receive, and a shorter arc duration means less total energy over time. The measured incident energy at a location is used to determine PPE and boundaries, and it directly reflects those variables.

Ambient temperature doesn’t enter the calculations for arc energy or the resulting hazard level. It can affect worker comfort or cooling of clothing, but it doesn’t change the arc’s energy delivery. So the environmental temperature is not a determinant of arc flash severity, whereas incident energy at the location, distance from the arc, and arc duration are.