A portable sampling unit capable of separating particulates, including biological organisms, from gaseous fluids such as air. A combined particle impact collector and fan is used to both move fluid through the sampling unit and to collect particulates. In one embodiment, the combined particle impact collector is a disposable unit that is removed and replaced with a fresh unit after each sampling period. The disposable unit is placed in a rinse station, where a liquid sample is extracted for later analysis. Alternatively, a disposable detection unit is incorporated in the sampling unit to provide real time detection of chemical toxins and/or biological pathogens. Preferably, the detector unit includes micro-fluidic channels so that a minimum amount of sample and test reagents are required. In another embodiment, the combined impact collector is integral to the sampling unit, rather than a separate disposable item.