Abstract: A closed hollow filter canister having gas-impermeable end walls (94, 96) and a gas-permeable side wall (100). Gas contaminated with liquid is sprayed under pressure through line (90) and flow-restricting orifice (80) into the interior space of the canister where the contaminants become atomized and are retained by the side wall (100). Gas free of liquid contaminants passes into the atmosphere. In a preferred embodiment the gas is air contaminated with water, and the wall (100) is of cellulosic material which becomes wetted with water which gradually volatilizes. The filter canister may be used to treat streams (90a, 90b) from a gas compressor (50) and an associated reservoir tank (125).