Natural ventilation is one of the most commonly used methods to remove air pollutants and to improve indoor air quality. This study integrates a resistance model to predict the ventilation rate and a transport model to compute the pollutant concentration in partitioned buildings. The model predictions are validated by a series of wind tunnel experiments with scale-down building models. The concentration variations of tracer gas inside the models were measured by a gas chromatography, and the external and internal pressures were determined by a multi-channel pressure scanner. The verified transport model was then applied to evaluate the influences of external wind speed, initial concentration, opening areas and interior volume on the transient concentration and dispersion time of gaseous pollutants within a two-room buildings. Results of the parametric study indicate that the dispersion time and the ratio of the maximum concentration in the adjacent room to the initial concentration of the room with the pollutant source was about 0.50–0.60, depending on the ventilation rate and interior volume.