This paper presents three case studies of air distribution systems. The three modeled case studies fall under the category of conventional air distribution systems. The study is performed by means of CFD Simulations.The position of air supply inlet is varied in each case. For each case, Air change per hour (ACH) is varied from 5 to 7. The objectives of this research were to (1) determine temperature distribution, velocity distribution, Humidity, contaminant concentration, and the Predicted Mean Vote (PMV) values in order to characterize the internal thermal environment for different air distribution systems, (2) study the effect of varying ACH on the thermal patterns, and the level of thermal comfort in the office space for the conventional air distribution systems.