The relation of the concentration dependence of the emf of low-temperature potentiometric gas sensors to the adsorption isotherms of the detected species is considered on the basis of the literature data and the experimental results of the,authors. The causes for the deviation of measured emf of the sensors from their theoretical values are discussed. The conditions for the formation of electrochemical products and their elimination from the triphase boundaries of solid electrolyte/electron conductor/gas are also discussed.