The j-box on the far wall looks similar to an Appleton GUBB catalogued at
http://www.appletonelec.com/pdf/K-2thru8.pdf The intent is not to stop hazardous vapors from entering, [that’s a loosing battle] but if contained vapors or gases ignite, then the threads or lapped surfaces “cool” the combustion products to limit high-temperature propagation outside the enclosure, reducing the chance of igniting airborne materials outside the enclosure.
NEC Chapter 5 wiring is a whole different animal and almost needs piecemeal assembly drawings to install correctly.
Petrochems, distilleries and NASA launch pads are unique in that regard. As can be imagined, the liability is tremendous.
