then I shall construct a leather bodysuit! airtight! and wear it with the magikal gas mask...
no, no I won't, but if gasses really are absorbed by the skin, one could, theoretically, make some sort of costume that could fit in period that could protect all skin, and finish it off with the period gas mask so that they could breath.
Im thinking plot would see to it that that person was justly delt with...as in, the idea not working and every other monster hucking about a gas globe, at him/her/it, out of spite