The present invention relates to a process fluid handling device in an electrochemical cell system having a fluid barrier between a process fluid compartment and a drive compartment of the fluid handling device. The fluid barrier comprises an interconnection compartment, filled with barrier gas. The pressure of the interconnection compartment is maintained above the process fluid and drive compartments, by fluid communication with barrier gas stored in a storage device. The barrier gas is preferably a non-reactive and dehumidified gas. The present invention also contemplates methods of isolating the hydrogen-containing process fluid in the process fluid compartment from the drive compartment, which is preferably in fluid communication with the ambient.