The Particle Streak Tracking System (PST) is a fast method to measure two- and three-dimensional velocity fields in room air flows with measuring areas up to 5 m2. The two-dimensional method works with a single pulsed white light sheet and one digital camera. For three-dimensional velocity measurements in planes a laser light sheet system using three separate laser sheets with two different wavelengths and two CCD-cameras is employed. To visualise the flow helium filled bubbles are used. A description of the set-up will be given and the data evaluation process will be explained.