NOVELTY - An organic contaminant molecule sensor includes an electrochemical cell having a solid state oxygen anion conductor, a measurement electrode, and a reference electrode; and a mechanism for monitoring the potential difference between the electrodes. The electrodes comprise a material for catalyzing the dissociative absorption of oxygen.    USE - For monitoring the amount of organic contaminant introduced into a monitored environment used in the semiconductor manufacturing industry.    ADVANTAGE - The invention provides a simple, low cost, semi-quantitative organic contaminant molecule sensor, which has a low sensitivity to unreactive organic compounds but can be used at the point of use to qualify the process environment.    DETAILED DESCRIPTION - An organic contaminant molecule sensor (10) comprises an electrochemical cell having a solid state oxygen anion conductor, a measurement electrode (14) formed on a first surface of the conductor for exposure to a monitored environment (18), and a reference electrode (16) formed on a second surface of the conductor for exposure to a reference environment. The electrodes comprise material for catalyzing the dissociative absorption of oxygen. A mechanism is provided for monitoring the potential difference between the electrodes, so that, in the absence of organic contaminant molecules in the monitored environment, the potential difference between the electrodes assumes a base value Vb and, upon the introduction of organic contaminant molecules into the monitored environment, the potential difference assumes a measurement value Vm due to the reaction of the organic contaminant molecules with oxygen in the monitored environment, Vm-Vb being indicative of the amount of organic contaminant molecules introduced into the monitored environment.    DESCRIPTION OF DRAWING(S) - The figure is a schematic cross-section of the inventive electrochemical sensor.    Organic contaminant molecule sensor (10)    Measurement electrode (14)    Reference electrode (16)    Monitored environment (18)    Reference environment (20)    Heater (22)    Thermocouple arrangement (24)