Abstract: A mixture of noble gases having desirable insulative properties for use as a window fill gas is derived from an air separation process without substantial further separation or concentration of the noble gases in the mixtures. The mixture of noble gases is processed to form the fill gas using relatively economical catalytic oxidation processes and drying techniques to provide a suitable fill gas. The processed noble gas or fill gas may contain from about 89 to 95% krypton, 5 to 8% xenon and 0.5 to 2% contaminants including oxygen, nitrogen, hydrocarbons and other constituents typically found in air separation processing.