30 CFR § 18.25 Combustible gases from insulating material.
(a) Insulating materials that give off flammable or explosive gases
when decomposed electrically shall not be used within enclosures where the
materials are subjected to destructive electrical action.
(b) Parts coated or impregnated with insulating materials shall be
heat-treated to remove any combustible solvent(s) before assembly in an
explosion-proof enclosure. Air-drying insulating materials are excepted.