3/10/2024 0 Comments Arc flash boundary labelWorkers without specialized training should stay outside of the boundary unless they have appropriate protection and are escorted by a qualified person. Qualified workers may cross this boundary after shock and arc flash risk assessments are performed with appropriate PPE if needed. The outer boundary at which a worker may be exposed to a shock hazard, the limited approach boundary, refers to the “stay back” distance for non-qualified workers. While the other two boundaries deal with shock hazard, the arc flash boundary refers specifically to arc flash hazards and explains that 1.2 calories/cm 2 of incident energy, is the distance at which a worker will receive second-degree burns in the event of an arc flash incident without appropriate arc rated personal protective equipment.ĭepending on the potential arc flash hazard, this boundary is calculated separately based upon specific system information or the boundary is determined in Table 130.7(C)(15)(a) and can be larger or smaller than the shock approach boundaries depending on the situation. Limited and Restricted Approach boundaries deal with shock and are determined by NFPA 70E Tables 130.4(C)(a) for AC systems and 130.4(C)(b) for DC systems, while Arc Flash boundaries are determined through an Arc Flash Analysis or through the use of the use of the Arc Flash PPE Categories in 130.7(C)(15)(a). As part of a larger training and safety program, these boundaries are put in place to minimize risk through avoidance or the use of PPE. These boundaries trigger multiple requirements in 70E including but not limited to determining the type and level of PPE and qualifications required to cross into each level. Under NFPA 70E, there are three boundaries that are observed-limited approach, restricted approach, (the shock protection boundaries) and arc flash boundary.
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