The ultimate purpose of this study is to quantitatively analyze the recirculation rate of pollutant($CO_2$) exhausted from the ventilation system in apartment units according to variables such as their shapes, the exterior direction of the wind, wind velocity, etc by performance of CFD and to present the entire analytical results as the utilization of the basic materials for the ventilation design. The result of the recirculation rate of pollutant in the apartment units has found that there was difference in the recirculation rate according to the analytical conditions. But it was analyzed that the average rate of it was about 4.3% and the maximum rate of it was 45.1%. When the external conditions such as wind and velocity were considered, double-wing type in 3.3% was analyzed as the best main building type on the ventilation efficiency among the four types of the main buildings, and single-wing type in 3.8%, flat type in 4.7%, and L-shape type in 5.2% are in the order of the efficiency.