Proper distribution of air in a ventilated barn is important in order to achieve satisfactory temperature and air quality in a swine barn. To design an effective contaminant control system in a conventional-flow type of swine barn, an understanding of airflow is most important. In this project, the FLUENT computer model was used to simulate the airflow pattern and ammonia concentration in a grower-finisher room. The predicted airflow was a three-dimensional patter. The three-dimensional flow structure, the contaminant concentration and temperature at the human breathing line (1.6 m above the flow) were highly affected by the combined jets, which were composed of a ceiling inlet, and the recirculation slot jet. The placement of the ceiling inlet and the recirculation duct affected airflow patterns, but had only a slight effect on the distribution of velocity, temperature and ammonia concentration along the human breathing line. Increasing the flow rate of cleaned recirculation airflow resulted in a lower ammonia contaminant level along the human breathing line. However, higher flow rates of cleaned recirculation air meant there would be higher fan operation and air cleaning costs. The optimum ratio of the ventilation rate tot eh cleaned recirculation rate appeared to be approximately 1:4.