Selective monitoring of indoor VOC at ppb level

Indoor air quality monitoring applications require both high sensitivity and selectivity, which are difficult to reach with solid state gas sensors. In particular, the discrimination between single volatile organic compounds (VOC) is generally not possible with stand-alone arrays of gas sensors. This limitation represents a major drawback, since not all indoor VOC are equally harmful for the human health. For this reason, a highly selective hybrid microsystem based on a gas-chromatographic-like (GC) approach is proposed. In this miniaturized GC system a solid state gas sensor is used as detector, together with a packed GC column micromachined in Si, a zero grade air unit, a minipump and a minivalve. With this prototype, Benzene, Toluene and m-Xylene eluted in synthetic or real indoor air were reliably detected and measured at concentrations as low as 5 ppb. Possible applications which could benefit of these performances include security control, air quality monitoring as well as food quality control.