Ppt level gas sensing by resistive gas Sensors: A review

Resistive sensors are highly popular sensors for the detection of toxic gases. This is mainly related to their high response, stability, compactness, low price and swift dynamics. In particular, most of them are able to detect toxic gases in ppm and ppb range. However, there are some reports about ppt level detection of gases by resistive gas sensors, a very low level close to capability of a trained dog. This feature is very important for increase of safety of our life and higher standards of life. In this review paper, for the first time we have discussed various sensing materials with ppt detection of gases. Mechanisms of gas detection are explained in detail. We believe that present review paper provides plenty of useful information for the researchers work in this interdisciplinary field.