Field chemical analysis (FCA) of volatile halogenated hydrocarbons is a highly debated topic of widespread interest due to the significant negative impact of these compounds on public health, on ecosystems and in the environment (e.g. destruction of stratospheric ozone). This article reports, for the first time, the use of a unique, lightweight (11 kg), man-portable membrane inlet mass spectrometer (MIMS) in the qualitative determination (for both detection and screening) and quantitative analysis of organohalogen chemical analytes in the gaseous phase. Representative compounds examined include: (a) volatile organochlorine compounds (e.g. trichloromethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,1,2-tetrachloroethane), (b) volatile organobromine and chlorobromocarbon compounds (e.g. bromomethane, dibromomethane, chlorobromomethane, bromodichloromethane), and (c) volatile chlorofluorocarbon and organoiodine compounds (e.g. chlorodifluoromethane, trichlorofluoromethane, 1,1,2-trichloro-1,2,2-trifluoroethane, methyl iodide). Gas phase experiments were undertaken at concentration levels from low ppb to low ppm. The results obtained exhibited excellent linearity within the concentration range examined, high sensitivity (limit of detection < 10 ppb), good repeatability (relative standard deviation, RSD < 5%) and membrane response times in real time (analysis within few seconds). Chemical investigations of mixture effects are also presented. Our method was successfully validated in laboratory based experiments within a test chamber.