Sensor system for indoor air monitoring using semiconducting metal oxides and IR-absorption

A sensor system for the simultaneous monitoring of CO2 and olfactory or explosive gases in room air is described. This system combines the functionality of semiconducting metal oxides and infrared absorption for gas detection. With the infrared radiation emitted by the heated metal oxide gas sensor an optical gas sensor for the CO2 detection is driven. Hence, the metal oxide gas sensor acts both as sensor for olfactory or explosive gases and as infrared source of the optical sensor. An experimentally validated model was set-up which describes the propagation of the emitted infrared radiation in the sensor system. Using the optical gas sensor the detection of 1000 ppm CO2 is possible with small cross-sensitivities to reducing gases which are caused mainly by reactions of gases with the heated metal oxide gas sensor.