An electrochemical cell for sensing gas has added mechanical support for the working electrode to prevent flexure of the working electrode due to pressure differentials. The added mechanical support includes: 1) affixing a larger area of the working electrode to the body of the cell; 2) a gas vent to a cavity of the body to equalize pressures; 3) a rigid electrolyte layer abutting a back surface of the working electrode; 4) infusing an adhesive deep into sides of the porous working electrode to enhance rigidity; 5) supporting opposing surfaces of the working electrode with the rigid package body; and 6) other techniques to make the working electrode more rigid. A bias circuit is also described that uses a controllable current source, an integrator of the varying current, and a feedback circuit for supplying a voltage to the counter electrode and a bias voltage to the reference electrode.