—This paper presents ventilation characteristics of naturally ventilated office room that conducted at University Putra Malaysia via 14 windows-door opening arrangements. Air Exchange rate, age of air and air exchange effectiveness of a naturally ventilated office were measured and evaluated, the amount of fresh air provided to the office for each condition was calculated. Tracer gas analysis, based on concentration decay method, is employed to determine these values. Air exchange effectiveness can be employed to characterize the ventilation air mixing within a room and greatly influences the indoor air quality. Age of air is an important index to evaluate indoor air quality in rooms. Experimental results showed that the office with windows-door opening configurations performed better than the opening closed office in terms of air exchange rate, age of air and air exchange effectiveness. The results indicated air flow patterns in the occupied zone which approximate “perfect mixing” in most conditions.
