Electrochemical properties of gas separators, holding a potential for the application in alkaline electrolysis, such as ionic conductivity and impermeability for hydrogen and oxygen gases, are significantly influencing the efficiency of alkaline electrolysis. Both non-zero gap and zero gap atmospheric pressure laboratory scale test set-up, operating at room temperature, were developed in order to undertake a comparative study of their advantages and disadvantages for the lab scale electrochemical characterization of gas separator materials. The zero gap cell was able to provide a more accurate ionic conductivity of the separators via Electrochemical Impedance Spectroscopy (EIS). The non-zero gap cell set-up, coupled with Quadrupole Mass Spectrometer (QMS), enabled the quantitative assessment of the oxygen crossover of different separators. The influence of a long term immersion in 25 wt. % KOH determined using the non-zero gap cell, showed increased conductivity with immersion duration for asbestos, while the highly hydrophobic PPS and PPS with PTFE separators' conductivity was not affected by longer immersion. (C) 2014 Elsevier Ltd. All rights reserved.