Which of the following is necessary to prevent second-degree burns from an electric arc flash?

To prevent second-degree burns from an electric arc flash, it is crucial to protect all exposed skin at incident energy levels greater than 1.2 cal/cm². This is because second-degree burns can occur when the skin is exposed to sufficient thermal energy, and 1.2 cal/cm² is a threshold that reflects the risk level for such injuries. Ensuring that all skin is adequately shielded helps to minimize the risk of severe burns in high-energy situations where electric arc flashes may occur.

The other options do not provide an effective means of preventing burns. Wearing fewer layers could actually expose more skin to potential harm, and open flames for testing pose their own risks, unrelated to arc flash protection. Minimizing exposure duration to electric arcs may reduce the likelihood of sustained injury, but it does not eliminate the immediate risk of burns caused by the thermal energy released from an arc flash. Therefore, consistent and comprehensive protective measures are essential in environments where electric arc flashes are a possibility.