What is the Arc Flash Boundary?

Simply put, the arc flash boundary is the distance at which an electrical arc can flash/expand outward, which may endanger employees working on electrical equipment. People that are not adequately protected must stay away from a potential arc flash source by this calculated minimum distance at all times.

NFPA 70E defines the arc flash boundary as “…a distance from a prospective arc source within which a person could receive a second degree burn if an electrical arc flash were to occur.”  In more technical terms, it is defined as the distance at which, in the event of an arc flash, a worker would be exposed to a thermal event with incident energy of 1.2 cal/ cm² for 0.1 second.  With this level of exposure, a worker may receive a 2nd degree burn to exposed skin.

If it is necessary for workers to cross the flash protection boundary, and potentially be exposed to higher incident energies from any arc flash, they must be wearing appropriate PPE.

The minimum distance is not common between different types of equipment. Some equipment will have a greater flash protection boundary while other equipment will have a lesser boundary.

The limited approach boundary

This is the minimum permitted distance that unqualified and unprotected personnel may approach a live component. Before crossing the limited approach boundary and entering the limited space, a suitably qualified person must use the appropriate PPE and be trained to perform the required work. An unqualified person may enter the limited approach area if they are under the supervision of a qualified person.

The restricted boundary

To cross the restricted boundary and access the restricted space, personnel need to have been trained in shock protection techniques, be wearing the correct PPE and have a written and approved plan for any work in the zone. The plan must make it clear that the worker must not enter the prohibited space or cross the prohibited boundary either personally or by using any equipment or tool.

Prohibited boundary (inner boundary)

In terms of safety, any worker crossing this boundary must be equipped and protected as they would be for making direct contact with the exposed live equipment.

Establishing these boundaries is an important step in protecting workers from the dangers of electrocution. No worker should cross the prohibited boundary and enter the prohibited area unless:

  • The responsible authority has carried out a full risk assessment.
  • The work has been documented and it has been fully established why it must be carried it out on live equipment.
  • The qualified worker has been trained to work on live electrical equipment.
  • The worker has been equipped with appropriate PPE.

To learn about the causes of an arc flash, read our article, What is an arc flash?

To see all of our NFPA 70E certified gloves and garments, visit our ARC FLASH page.

 

Related Articles

To learn about the causes of an arc flash, read our article, What is an arc flash?
To see all of our NFPA 70E certified gloves and garments, visit our ARC FLASH page.
To learn what gear to wear to protect youself, look at our guide to NFPA 70E Standard for Electrical Safety in the Workplace

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(800) 527-3826
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10747 Norwalk Blvd.
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(800) 527-3826
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