We measured the air exchange rates (AER) in up to six rooms in five naturally ventilated dwellings across four seasons using active tracer gas. Night time AER was also estimated in all bedrooms based on occupant-generated CO 2 . Additionally, we studied the pollutant distribution across the dwellings and airflows between rooms. AERs changed rapidly during the day and differed between rooms. Occupant behavior (window opening) strongly influenced the AERs. AERs were highest in the summer, lowest in the winter. Interzonal airflow measurements indicated that the air within a given floor is well mixed, while there is less air movement between different floors. The position of the internal doors (open/closed) had a strong influence on the air movements within the dwelling.