Clinical studies in recent times confirm feasibility of using trace concentrations of volatile organic compounds (VOC) in human exhale air as potential bio-markers for a variety of disease states. A Differential Mobility Sensor (DMS) with dual ultra-violet (UV) photo-ionization source is proposed and demonstrated for measurement of trace amounts of VOC gases in human exhale air. Experimental work performed with the DMS using high frequency asymmetrical waveform field for detection of trace concentrations of acetone and hexane with a few carrier gases including air, CO2 and O2 is discussed. The detection limit as estimated for Signal to Noise Ratio (SNR) of 3 is of the order of sub ppm levels for acetone and hexane. Experimental studies clearly demonstrate selective sensing of a gas in a mixture of gases by applying appropriate compensation field. Preliminary study on sensing of acetone in human breath shows good a correlation with blood glucose measurements.