Electric fault arcs occurring with short-circuits in electric power equipment and installations are enormous sources of power. There are particularly thermal effects (radiation and convective heat flux, metal splash) with high risks for persons especially in case of direct exposure, e.g. during live working or working in the vicinity of live parts. Personal protective equipment (PPE) can essentially contribute to increase the personal safety. The selection of protective measures or the assessment of their efficiency requires a risk analysis. Since the thermal arc hazards are proportional to the electric arc energy as well as the incident energy in the exposure distance, the risk assessment has to be based on the energy conditions. The electric arc energies to be expected in the electric power systems (working places) under consideration have to be determined as well as the equivalent energetic protection levels of the PPE. The paper gives an algorithm for analyzing the thermal arc risks for finding the necessary protection class of PPE according to the box test levels for protective clothing (IEC or EN 61482-1-2). Interconnections to the influence of the electric protection devices are shown.