Abstract: A process is disclosed for the cryogenic purification of industrial by-product gas streams containing recoverable hydrogen. Two feed streams, one of which contains non-readily condensible compounds having boiling points below that of methane, are passed through a successive series of cooling and separation stages. A condensed bottom fraction is separated in a separation drum from an overhead of increasing purity at each stage, and the condensates are combined into one or more condensate streams. The overhead from the stream containing the non-readily condensible compounds is injected into a combined condensate stream, reducing the temperature thereof, and the combined condensate stream is passed back through the heat exchange means to provide refrigeration for the system. An increased amount of hydrogen product is thereby recovered.