gas-proof (1)youdaoicibaDictYouDict
"Impermeable to (especially poisonous) gas; gas-tight", Mid 19th cent.; earliest use found in Boston Daily Atlas. From gas + proof.
gas-proof (2)youdaoicibaDictYouDict
"To make (an enclosure, material, etc.) gas-proof", Mid 19th cent. From gas-proof.