Arc Flash Boundaries - 2015
Arc flash labels produced to the NFPA 70E 2015 arc flash standards have three defined boundaries: two are shock protection boundaries and the outer flash protection boundary based on calculations of the incident energy calculations and maintenance of the electrical equipment affected.
Flash Protection Boundary - This is the outermost boundary, furthest away from the energy source of the potential arc flash hazard an unqualified person can approach unaccompanied. An unqualified person may only cross this boundary accompanied by a qualified worker. Should an arc flash occur, the person exposed to the blast would be subjected to the heat generated by the flash resulting in second degree burns (1.2 calories/cm2) which is typically curable. At this distance PPE must be worn to prevent 2nd degree (or greater) burns if exposed to the arc flash.
Limited Approach Boundary - Only qualified persons within this boundary. This is the distance an unqualified person may enter when continuously accompanied by a qualified worker, wear the appropriate level of PPE and trained for the task.
Restricted Approach Boundary - Shock Protection and Flash Protection. This boundary is restricted to unqualified personnel. Only a qualified worker, wearing the appropriate level of PPE and properly trained for the task to be performed may enter this area. It also requires an approved work permit with a written plan of the task to be performed. The written plan should include well defined procedures to prevent exposure to shock hazards in the Restrictive Approach Boundary.
As stated in NFPA 70E 2015 Article 130.4(D) Restricted Approach Boundary:
This applies to working on systems that have exposed energized electrical conductors or circuit parts that are operating at 50 volts or more.
Complete the Quiz Me activity below.
Figure 1: Arc Flash Boundaries 2015