A dust-trajectory technique for flow velocity measurement in a compressible medium is discussed. The technique consists of suspending zinc stearate powder in the compressible medium. The dust particle is illuminated by an intense light flashed at a desired frequency. The dust trajectory is photographed and analyzed to determine the flow velocity. Three sample tests were used to demonstrate the utility of the technique. Errors of the method were also analyzed that show the dust trajectory being truly representative to the fluid motion. Errors are resulted primarily from the measurement of length and rpm which could be analyzed in a traditional fashion. The method is particularly suited for flow measurements in small spaces in which most present techniques are handicapped. Given the available light source and film speed, the method works best in the medium velocity range.