Abstract: Water contamination is purged from molecular sieve material used in oxygen concentrators by heating the molecular sieve material to a temperature in the range of approximately 450.degree. to 950.degree. F., and subjecting the molecular sieve material to a stream of dry sweep gas having a dew point in the range of approximately -80.degree. to -100.degree. F. In the preferred embodiment, the molecular sieve material is contained in a vessel and heated by means of a number of heating elements. In addition, a flow of dry sweep gas is produced by at least two drying chambers containing a desiccating material. A first valve assembly alternately cycles the sweep gas through the first drying chamber and then through said second drying chamber.