Junction Box Rules

I'm not sure what you are asking in your question. If you are asking if a nema 4x junction box can be used in a classified area the root answer is yes. The box itself is not the issue though is it? It's the equipment you put inside the box that makes the difference. If none of the devices in this junction box are arcing devices, it can still be installed in your classified area. If there are arcing devices present the box either needs to be explosion proof or you need to purge the box to insure the presence of ignitible gases is non-existant.

I am in england and we work to the Atex directive for hazardous area... Normal I/P protected junction boxes can be used in a hazardous area if they only contain intrinsically safe ciruits... the barriers or galvanic isolators must be located in the safe area.. these junction boxes should be labelled up as containing intrinsically safe circuits and all cables should be with a blue outer sleeving to identify they are intrinsically safe circuit / loops. All other equipment should be certified for hazardous area use and be either flameproof or increased safety.. which are the common means of protection. They must all be certified for the area zones, the failure T temperature and the gas / dust type. Hope this helps as i have no idea from your question what equipment is being installed.