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Components normally need to be rated for the area, that are within the area. Electrical boxes $$
Conduits need to be sealed off, check current regulations. NO EMT all ridgid
Look into GN2 purging, positive 1 atmosphere. Power shutdown if lose of the purge.
Intrinsic safety barriers.
4-20 ma Low Voltage instrumentation and controls thru intrinsic barriers.Did a large instalation at a NASA site a few years back.