Abstract: For identifying one of a plurality of known gases in a gaseous mixture ba on air a single catalytic transducer is placed in the gaseous medium. The catalytic transducer is heated to a lower threshold temperature at which the oxidizable gas is oxidized little or not at all and a first value of a parameter characteristic of the thermal state of the transducer is captured. The catalytic transducer is then heated to an upper threshold temperature at which the oxidizable gas oxidizes significantly in contact with the catalytic transducer and a second value of the parameter characteristic of the thermal state of the transducer is captured. Using a predetermined law, a response signal representative of the gaseous medium is produced from the difference between the second and first values of the parameter characteristic of the thermal state of the catalytic transducer. The catalytic transducer is allowed to cool below the lower threshold temperature and the above operations are repeated cyclically.