I am confused and would value you thoughts. In the current version (2009) of NFPA 60e, the AFPB is now defined as a "distance from a prospective arc source" - whereas previously it used to be a distance from exposed live parts.

However - does the evidence not indicate that in reality the arc flash HAZARD really only exists when the conductors are exposed, for example when the panel covers are removed or work/interaction is being done? Most equipment, if designed and built to the correct standards, should contain the arc flash within the closed compartment? Therefore, is it "safe" for work to proceed - for example on "dead" Category 0 equipment in close proximity to closed "live" Category 4, if there is no interaction with the latter?

Your help would be very much appreciated!

Equipment is not intended to contain an arc flash, unless it has been specifically built that way.

However, according to an NFPA70E-2009 FPN to the definition of Arc Flash Hazard, operating properly applied and maintained equipment is unlikely to cause an arc flash, therefore there is nothing to be contained.

I would not be surprised to find that a high percentage of electrical equipment is not properly maintained and as such may present a hazard.