An arc flash boundary represents the distance an arc flash can travel as well as the distance from an arc flash hazard that will cause severe injury or damage. The National Fire Protection Association has identified three different types of arc flash boundaries and these boundaries are rings around the hazard itself. The different boundaries are as follows:
→ Prohibited: This boundary ring is the closest to the hazard or energized equipment. It requires high levels of PPE for workers in this area and only qualified and train employees should be allowed in this area.
→ Restricted: Between the prohibited ring and limited ring is the restricted boundary. Again, it warrants only trained and qualified workers to enter and both PPE and shock protection equipment should be used.
→ Limited: The furthest boundary from energized equipment is also the safest boundary. Safety practices however, should not be ignored. This includes proper training and PPE.
An excellent way employers or safety managers can improve arc flash safety is to clearly mark off the boundary with floor marking tape. This is a great visual reminder that anyone working within the boundary will need to don appropriate personal protective equipment.