Electrolytic cells based on stabilized zirconia as a solid electrolyte may be used to remove oxygen from stationary or streaming gas. The minimum pressures (activities) that can be accurately measured are limited by the onset of electronic conduction in the electrolyte. In buffered gases, the lowest pressure that can be attained either by the capacity of the buffer or by the decomposition kinetics of the buffer molecules. Typical values of the oxygen pressures that can be reached when using commercial high‐density sintered stabilized zirconia tubes as an electrolyte, are Equation or symbol description not available≈10−38 atm at 530°C, Equation or symbol description not available3×10−30 atm at 700°C, and Equation or symbol description not available3×10−27 atm at 800°C.