An investigation on the thermal comfort level of a naturally ventilated office room with fourteen windows-door opening arrangements as a function of maximum, minimum and mean air exchange effectiveness (AEE) has been conducted. The tracer gas decay method has been applied during the experimental procedures to estimate air exchange effectiveness, on the basis of room mean and local age of air. Thermal comfort variables have been measured and through these data, Predicted Mean Vote (PMV) and Predicted Mean Vote (PPD) have been calculated. This study has shown that there are relationship between AEE and thermal comfort and three linear regression equations of PMV versus AEE can be derived for this office.