The influence of CO2 on the oxygen permeation performance of perovskite-type BaCoxFeyZrzO3-delta (BCFZ, x + y + z = 1) hollow fiber membrane under different experimental conditions is presented. Helium with various partial pressures of CO2 was applied as sweep gas at different temperatures on the shell side of the hollow fiber leading to a decrease and finally drop to zero of the oxygen permeation while feeding air on the core side due to carbonate formation. Repeated cycles of changing the sweep gas between the CO2/He mixture and pure He were conducted in order to check the reversibility of the carbonate formation. The analysis of the microstructure after permeation experiments was carried out by X-ray diffraction (XRD) as well as by scanning electron microscope (SEM). It was found that both microstructure as well as oxygen permeation are recovered in a CO2-free atmosphere like pure He on the shell side while feeding air on the core side. Under exposure of 50% CO2 in He for 5 h, the perovskite structure is impaired up to a depth of ca. 15 mu m and approximately 30 mu m after 10 h, respectively. (C) 2010 Elsevier B.V. All rights reserved.