How To Calculate Arc Flash Boundaries - EPSCO


Creating a comprehensive approach to electrical safety at your facility can feel like a project that’s too massive to take on, especially when you have deadlines and budgets to meet. 


At EPSCO, we see electrical safety as a step-by-step process, and a key component is understanding hazard boundaries. With properly established boundaries and barricades, anyone working around electrical equipment will know how to maintain a distance that minimizes the risk of electrical shock. Let’s take a look at how to calculate arc flash boundary.


Conducting an arc flash study is the FIRST STEP in determining boundaries. Incident energy levels are calculated for each piece of equipment, defining the potential arc flash hazards’ energy release and blast radius. 

AF Labels


NEXT, boundaries are determined. The Flash Risk Boundary is based on the distance from the arc source that a person could be standing and suffer second-degree burns during an arc flash event. The Limited Approach Boundary is determined by the distance from an exposed energized conductor or circuit part within which a shock hazard exists.  Keep in mind that the arc flash boundary depends on the level of fault current available in the equipment, while the limited approach boundary is fixed based on the equipment’s voltage.  These two boundaries exist completely independently of each other.



FINALLY, once boundaries have been determined, it’s time to place barricades. To properly barricade, take the greater distance between the arc flash boundary and the limited approach boundary, then set the barricades at or beyond that distance when working energized.



Barricades are used to warn workers of potential electrical hazards and limit access for workers who are unqualified to be in areas where there is energized work. 

There are many effective and recognizable barricades, including:

     — Tape

     — Cones

     — A-frame wood or metal blockades


**Only qualified workers who have received the appropriate training and are wearing properly rated PPE should access areas beyond the barricades**


By understanding how to calculate arc flash boundary, you can determine proper working distances to keep everyone on your team safe.


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