A gas measurement system (100), of this invention includes a housing (250) adapted to be mounted on an airway adapter. An infrared absorption gas measurement assembly (240) and a luminescence quenching gas measurement assembly (236) are disposed in the housing. A processor (510), also disposed in the housing, is programmed to measure gas constituents of a gas flow in the airway adapter based on an output of the infrared absorption gas measurement assembly and the luminescence quenching gas measurement assembly.
