Explosion Proof pipe

[John165]

I was told that pvc pipe can be used on explosion installation, if the pipe going down to it is IMC if so how deep? I tried looking in art 500 but couldn't find any thing.

 

[Elect117]

501.10 (A)(1)(1) exception

2in concrete encasement + 24in of top cover over the conduit and must be threaded steel IMC or RMC where it emerges from grade.

There are other specific sections that might have other requirements. Like gas dispensing facilities.