Abstract: A device sensitive to a combustible gas having an exothermic oxidation reaction comprises a catalytic element in the form of a body of material a major proportion of which consists of an aluminosilicate zeolite having a ratio of silicon to aluminum of greater than two and a three-dimensional pore structure; a catalyst metal within the zeolite pores; and heating means for heating the catalyst to temperatures at which it will cause combustion of the gas.

Abstract: In a system for monitoring the composition of exhaust gases from an internal combustion engine, a gas-sensitive resistor consisting of gallium oxide is exposed to the gases and is maintained at a substantially constant temperature above that of the gases. A signal is generated dependent on the resistance of the resistor, which varies monotonically with the air/fuel ratio of the inlet mixture, this signal being usable in a system for automatically controlling the composition of the inlet mixture.

Abstract: In a catalytic method for selectively detecting carbon monoxide in the presence of hydrogen in an oxygen-containing atmosphere, such as may be used in monitoring exhaust gases from combustion processes, the catalyst is a platinum-rhodium alloy containing not less than about 10% rhodium. The catalyst is maintained at a temperature such that it will cause combustion of carbon monoxide but will not readily cause combustion of hydrogen, the thermal effect on the catalyst resulting when a test atmosphere is brought into contact with it being sensed to provide a measure of the carbon monoxide concentration in that atmosphere.