In the oil and gas industry (working around hazardous areas), I commonly see conduit seals in places that they should not have been installed, but not being able to wait for the conduit to be re-done due to project startups, the seals are left as they were installed. Oftentimes, these do not get poured since they were unnecessarily installed in the first place (justs costs extra money to install them). I've had a few electrical inspectors mention that the NEC code requires these seals to be poured if they are installed, but I can't seem to find evidence within the code to backup this claim. Any help or suggestions?