An apparatus for separating and recovering effluent gases from a furnace includes a pressure vessel for containing the gases. This vessel has a fluid input for receiving the gases and a fluid output for selectively removing the gases when they are separated. A condenser is provided to transform and maintain the lowest vapor pressure gas as a liquid so that it accumulates as a liquid at the bottom of the vessel. The remaining non-condensed effluent gases accumulate in strata above the liquid. Apparatus is provided to selectively remove the liquid and at least one of the remaining non-condensed gases from the vessel through the fluid output. Also set forth is a method for recovering effluent gases from a furnace including the steps of adding the gases to a pressure vessel, altering the density of the gases so that the lowest vapor pressure gas condenses into a liquid and the non-condensed gases stratify above the liquid. Then the liquid is removed from vessel and optionally expanded to cool the vessel. Finally, at least one stratified non-condensed gas is selectively removed from the vessel.