The objectives of this research were to predict contaminant concentration distribution in occupied zone and contaminant removal efficiency as a function of an occupied zone obstruction level, air distribution method, air change rate, cooling load and contaminant source non-uniformity. The final objective was to develop a concentration variation coefficient to be used for design of air distribution systems. Concludes that the room air distribution method results in contaminant concentration non-uniformity inside the occupied zone. A method was developed to take this into account during the design of air distribution systems. The influence of air distribution method, air change rate, level of room obstruction and cooling load, on occupied zone concentration uniformity and contaminant removal efficiency were studied. Their influence was found to be small. Non-uniform distribution of the contaminant sources inside the room was found to have the biggest influence on the studied measures. However, the influence is unique for each air supply method, and their ability to eliminate the influence of the non-uniformity varies greatly.