16.) Portions of raceways installed connecting varying temperate atmospheres without vapor transfer seals
300.7 Raceways Exposed to Different Temperatures.
(A) Sealing. Where portions of a raceway or sleeve are installed and subjected to different temperatures and where condensation is known to be a problem, the raceway or sleeve shall be filled with an approved material to prevent the circulation of air through the raceway or sleeve. The section does not require the seal to be explosionproof.