and more than one secondary oxygen separation element 26 could be provided there are preferably between 7 and 15 of the primary oxygen separation elements 18 in any application of the present invention and a single secondary oxygen separation element 26 the applied voltage across all such elements is preferably between about 1 3 volts and 1 7 volts the current passing through each of the primary oxygen separation elements 18 and the secondary oxygen element 26 could be between about 0 and 20 a under such circumstances the oxygen content of the gas stream 10 can be between about 0 1 percent and about 2 percent and the partially purified stream exiting the first separation zone 14 can thereby have anywhere from between 100 and 200 ppm oxygen the secondary oxygen separation element 26 the purified stream 12 can be discharged by less than 10 ppm this assumes feed has a flow rate of between about 10 and about 100 standard liters per minute and a pressure of about 100 psig as indicated above the connection of a ceramic element to a metal such as primary oxygen separation elements 18 to the inlet and outlet manifolds 20 and 22 and the secondary oxygen separation element.