A number of new monitoring techniques for characterizing hazardous air pollutants have arisen in response to the limitation of standard batch methods. Based on mass spectrometry and direct air sampling interfaces, the techniques measure all of the target analytes in a sample simultaneously without prior sample preconcentration or chromatographic separation. Those based on the ion trap mass spectrometer (ITMS) offer a powerful means of developing compact, field-deployable systems with high sensitivity, specificity, and speed for continuous real-time monitoring of volatile organic compounds (VOCs) of environmental interest in air. The necessary specificity is provided by tandem mass spectrometry (MS/MS) in which parent ions are isolated selectively before undergoing dissociation to form characteristic product ions.