Abstract: Apparatus and method for separating condensible vapors from a gas mixture. The apparatus may include an expansion chamber of circular cross section, one end of which terminates in a converging nozzle section; a tubular separator connected to the expansion chamber, the walls of which have perforations therein; and a diffuser chamber of circular cross section, the entrance of which is a diverging nozzle section. Relatively high pressure gas and condensible vapors are introduced into the expansion chamber for isentropic expansion, cooling and increase of velocity thereof by passing through the converging nozzle. The cooled gas and entrained liquids, resulting from the cooling thereof, are passed through the tubular member, the entrained liquids passing through the perforated wall thereof for separation from the gas. The gas from which the liquids have been separated are then isentropically compressed by passing through the diverging nozzle section for exhaust through the diffuser chamber.