Oxygen separation technology has applications in health care, defence, on-site generation of gases with known oxygen concentration, food packaging (oxygen removal), aquaculture and a number of others. The market potential for this technology is of the order of several billion dollars globally. Ceramic membranes based on O2- or O2-/electronic conducting materials have the potential to service this market. Pure O2- conducting ceramic membrane technology can be used not only for production of oxygen but also for oxygen removal in gas streams and enclosures as well as for oxygen level control to produce calibration gases, In this paper, the operation of several oxygen separation devices of tubular design constructed from zirconiayttria electrolyte has been discussed for oxygen generation, oxygen removal and control. Life time tests performed for periods up to 8000 h have been described.