While most of are aware of the term "arc in a box" and the term seems to be self-explanatory, I have to ask is there and in what document is it officially defined?

NFPA 70E, IEEE 1584, NESC, OSHA 1910.269, all refer to it in some manner and in similar context to an arc flash that occurs inside an enclosure of some type versus in open air, I'm unable to find an official definition of this very commonly used term.

Many of the documents listed above point back to "Doughty, Neal, and Floyd, 'Predicting incident energy to better manage the electric arc hazard on 600 v power distribution systems'".

I've also found a few unofficial definitions out there on the web but they don't point back to a source for their definition.

In an 'arc in a box' the incident energy is reflected or focused in the direction of the opening, which is usually towards the employee. Probably 99% of indoor industrial locations are' arc in a box'
In 'open air' the incident energy is spread uniformly in all directions. About the only true open air locations are conductors and switches on poles.

Thanks JBD,

I'm aware of what an arc in the box is, the equipment associated with it and the arc flash hazard compared to open air. However, I'm asking if anyone is aware of an official definition contained in a standard somewhere.

The 2002 Edition of IEEE 1584 mentioned enclosed equipment 4 times in the main text but never defined it as it was implied.

The 2018 Edition of IEEE 1584 uses the word “enclosed� 8 times in the main text and the word “enclosure� is used 165 times. However, a formal definition of “enclosure� or “enclosed� is not provided.

There are descriptions in the text such as Annex G The metal enclosures used in the test are with an open front end. Also, photos of the enclosures “boxes� are provided including VCB, VCBB and HCB and dimnesions are provided but no "official" definition. other than under "electrode configuration"

Thanks Jim for the references.

But I was wondering if an official definition for "arc in a box/arc in an enclosure" and "arc in open air" is warranted in IEEE 1584 and/or 70E? Or do you think it's not necessary?

George: Now that you pointed it out, it might not be a bad idea. Especially in IEEE 1584 since that is where is is most directly used. Nothing on the radar screen for a 3rd edition yet but when that time comes, this might be good to add. Thanks

So Jim, it sounds like to me that you just made a commitment on this forum that you'll be submitting the idea for a definition of Arc in a Box to be added to the next revision of IEEE 1584??

That's what I love about you buddy, you see or hear of a problem and you take the bull by the horns and "own" the solution.

Besides you really don't want me making a proposal to IEEE 1584 for two reasons: First I'm not a smart engineer but only an electrician, hence the last 'E' in the acronym IEEE and Secondly, of all public inputs I've submitted to 70E, they've only accepted two of them over the years. So I have a horrible track record getting my suggestions implemented.