Ryan -
We ran into similar issues, and as Dehner and Equinox suggested, we had to get very comfortable with our local electrical inspector (who is a bit difficult to work with AND hasn't had to deal with this type of industry ever before). In the end, prior to installing anything, the inspector requested a formal code review and engineers stamp by an outside agency (which cost around $1500). It was expensive, but once we had that in hand the inspector backed off (for now, we still need our final electrical inspection). Our requirements did include localized areas of the plant that are Class 1 - Div 1 and 2 and needed XP / NEMA 7 motors, enclosures and conduit.
The codes referenced in our review were NFPA and Massachusetts state building code (MSBC), which is built off national el. code (NEC).
This was in MA, so all requirements and inspections fall on local municipal government - the state gov stays out of the process. Other states may require approval at state/county and municipal level - but your local inspector should be able to tell you that.
ALSO keep in mind, as mentioned above, these are minimum requirements - I would highly recommend going the extra mile to keep yourself safe and the inspector comfortable. We installed an additional environmental hydrocarbon sniffer, over sized ventilation fan and a number of process monitoring devices that have built in fail-safes should any of our equipment malfunction. Small price to pay for a much larger piece of mind.
Good luck!