Eight mechanically ventilated flow patterns have been conducted in a test chamber. The air age in test chamber is measured with tracer gas technique. A CFD program named as STACH-3 is developed with the transport equation of air age in it. The predicted air age with STACH-3 is compared with the experimental results. It is shown that the computed air age agrees well with the experimental results except a few points. The relationship between flow pattern and air age distribution for the test chamber is analyzed with not only the predicted but also the experimental results.