A novel and simple technique has been developed for experimental modeling of buoyancy -driven building ventilation airflows . In this technique, fine electrolytically generated hydrogen bubbles function as buoyancy sources to simulated heating elements in buildings and, at the same time, as the tracers for the flow field. Experiments showed that the displacement natural ventilation in single-zone building induced by a line buoyancy source was well reproduced using this new technique, It is demonstrated that compared with existing modelling techniques, the fine bubble approach is simple, economical and compact.