Oxygen permeation through Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCFO) perovskite tubular membranes was investigated under vacuum and elevated pressures conditions. This paper is focused on dependence of oxygen permeation flux on oxygen recovery, temperature and feed pressure. Oxygen flux decreases with the raise of oxygen recovery, more quickly when the recovery is larger than about 60%. Elevating the feed pressure speeds up the decrease of oxygen fluxes against oxygen recovery. Oxygen permeation flux increases with the feed pressure of air, however, the increment decreases gradually. Oxygen permeation flux and recovery increase with temperature gradually at a constant airflow rate and pressure. The permeation flux reached 9.5 cm(3)/cm(2) min at an oxygen recovery of 48% under the condition of 925 degrees C and vacuum pressure of similar to 100 Pa for permeation side and 7 atm for feed side. Long-term operation under vacuum and elevated pressure shows that oxygen purity larger than 99.4% can be obtained when silver was used as sealant. (C) 2009 Elsevier B.V. All rights reserved