The human body emits various volatile molecules, depending on a person's genetics, stress, disease and so on. The volatile organic compounds (VOCs) can be found in human transpiration, breath and transdermal gas emanated from skin. In this review, a biochemical gas sensor “bio-sniffer” and a gas imaging system “sniff-cam” for monitoring of VOCs such as acetone, ethanol and acetaldehyde were presented. Firstly, a high-sensitive acetone biochemical gas sensor was demonstrated and measure exhaled breath acetone concentration, and assess lipid metabolism based on breath acetone analysis. Secondly, a fluorometric imaging system for ethanol vapor released from human breath and palm skin was presented. This imaging system measures ethanol vapor concentrations as intensities of fluorescence through an enzymatic reaction. These biochemical gas sensors and imaging system of VOCs showed a rapidly and accurately responses and measurement, which could lead an analysis to metabolism function and non-invasive screening at real time in the near future.