In this paper, baffles were used as a solution to the stratification problem. Computational fluid dynamics (CFD) has been used to simulate a specific air handling unit with outside air passing straight through the mixing chamber and the outdoor air entering the mixing chamber perpendicular to the outside air. Mixing characteristics such as thermal statistic and range mixing effectiveness of two baffles have been investigated. The influence of the baffle size and angle on these characteristics was studied and compared to the results of a case with no baffle. The results show that when both the Outside Air Baffle and the Return Air Baffle are used results show no progress in mixing characteristics when the angle of the baffles equal 0°. However, increasing the angles of the return and outside air baffles resulted in an improvement in the mixing characteristics. The relationship between the pressure drop and mixing effectiveness was plotted for all cases in order to determine the best case that leads to good mixing characteristics with a small pressure drop