This article presents experiment data on the preferential CO oxidation (PROX) in a hydrogen-rich stream, currently the most practical method for CO removal induced by a double-stage process. The reaction was carried out in a microreactor testing unit using Au and Pt supported on an A zeolite catalyst in the temperature range of 50-300 degrees C under atmospheric pressure. The reactant gas Mixture contained CO (1%), O-2 (1%), H-2 (40%), CO2 (0-10%), and H2O (0-10%), with the balance being He, at a total flow rate of 50 mL/min. The results clearly show that the addition of the second stage significantly reduces the H-2 loss and the O-2 requirements while greatly increasing the CO selectivity from similar to 48 to similar to 58%. The addition of CO2 and H2O in the feed slightly reduces the CO oxidation activity both in single- and double-stage processes. Moreover, the double-stage process shows a CO removal efficiency of over 99% during 60 h of testing at a reaction temperature of 170 degrees C in the Simulated reformed gas (CO2- and H2O-free).