A system based on expert systems and ion trap mass spectrometry has been developed to monitor air quality for life support applications. Three different analytical techniques, Thermal Desorption/Gas Chromatography/Mass Spectrometry (TD/GC/MS), Gas Chromatography/Mass Spectrometry (GC/MS), and Mass Spectrometry/Mass Spectrometry (MS/MS), were implemented on this system and evaluated with respect to their potential utility for monitoring major atmospheric constituents, trace levels of known contaminants, and trace levels of unknown compounds in closed environments. TD/GC/MS is an excellent method for characterizing ultratrace levels of volatile organic compounds (VOC's) and has been employed for off-line analysis of air samples collected during several space missions. GC/MS is perhaps the most commonly used method for the analysis of complex mixtures and is currently under development for on-line monitoring of trace contaminants for the space station. MS/MS is a relatively underutilized method which shows excellent promise as a developing technology for real-time monitoring of air quality for long term space missions. The development, implementation, and characterization of ion trap mass spectrometric methods based on these three techniques are compared and contrasted for life support monitoring applications.