Abstract: Traditional solution of ventilation rates with the concentration change is based on a one room ventilation model. From the equation of mass balance of tracer gas, the ventilation rates of the cabin(multi room) can be solved by using sigle tracer gas measurement or multi tracer gas measurement. For improving the air quality, the concepts of age of air are introduced and the solutions of age of air and ventilation efficiency are obtained by using tracer gas concentration of typical points of the cabin.

Key words: t racer gasmethod, vent ilat ion rates, age of air, mult izone infilt rat ion