Abstract: A vapor component of a gas mixture is separated by condensation and is recovered for further use. A solvent vapor mixed with inert gas is condensed in a multistage heat exchange system in a manner which utilizes a first refrigerant to condense a portion of the vapor in a first heat exchange device, a second refrigerant, typically cold inert gas, for condensing a further portion of the vapor in a second heat exchanger and a third heat exchange device wherein chilled liquid is utilized to condense a still further portion of the vapor. In a fourth heat exchange device, a cryogenic liquid is passed in heat exchange relation with the liquid passed thereto from the third heat exchange device. The cryogenic liquid is vaporized to form an essentially pure inert gas which is supplied to the vicinity of the oven exit and entrance, but exteriorly of the oven to form inert gas barriers. The fourth heat exchange device may effect direct or indirect heat exchange with the cryogenic liquid.