Approach Limits

The NFPA has defined boundaries around electrical equipment that organize the level of hazard that equipment presents. The closer a person gets to a piece of equipment, the greater the hazard of arc flash or other dangerous electrical events. Approach boundaries take into account the hazard analysis findings for equipment and provide an idea of the safety practices, protective equipment, and qualification required at various distances. These boundaries govern safety practices for both "live" and de-energized equipment.

The flash protection boundary is typically the outermost limit for a piece of equipment. The IEEE defines this boundary as the distance from live, un-insulated, or exposed parts at 50V or more within which a person could receive a second-degree burn from an arc flash. This is the closest that both qualified and unqualified workers may come without wearing arc flash protective equipment.

The limited approach boundary is the distance at which a shock hazard exists. Unqualified workers are prohibited from crossing this boundary without an accompanying qualified person. Personal protective equipment is required to enter this boundary.

The restricted approach boundary is the distance within which there is an increased risk of electric shock. Unqualified persons are prohibited from entering this boundary. In the event of an arc flash, electric shock and third-degree burns are likely at this distance for any person without the proper protective equipment and insulated tools.

Because electricity can move through the air, this proximity to equipment poses serious danger of an arc flash and working within the restricted approach boundary is considered to be the same as making direct contact with energized parts. Qualified workers entering this area must meet strict safety requirements, including possession of a detailed plan justifying the need to work in the boundary, demonstration of a full understanding of the hazards involved, and use of protective equipment on all body parts while inside the boundary.

To learn more about Arc Flash Safety visit our OSHA Construction Arc Flash Safety Online Training web page.