THHN Wire in a C1D1 installation

[Dale Samuels]

I work in the distilled spirts industry and we have many classified areas. A member of our engineering group was told by an engineer from a chemical company that they did not allow THHN/THWN insulation to be used in their facility because there could be vapor passage between the inner PVC insulation and the outer thermo-plastic covering. I know there are issues with shielded cables, but I have never heard of any issues with individual wires. Thanks for the help!

 

[rbalex]

I guess we can give it a few points for style and originality, but it gets zero for accuracy. PVC is thermoplastic, the jacket is nylon, the "problem" described is silly.
And, if you are having problems with shields, you need to review 501.15 (D)(1) Exception and 501.15(E)(1) Exception 2.