In this research, the airflow pattern and particle dispersion in a contaminated full-scale cleanroom are investigated numerically using both Eulerian and Lagrangian approaches. Three different supply diffuser configurations namely (1) central, (2) horizontal and (3) vertical and three different exhaust grille configurations namely (4) vertical symmetric, (5) asymmetric and (6) horizontal symmetric are selected for the analysis. The presented results reveal that the supply/exhaust openings arrangement has a significant influence on the particulate contaminant dispersion in the cleanrooms. The comparison of the above different supply diffuser configurations shows that the vertical and horizontal supply diffuser configurations lead to a more escaped particles and less deposited particles on the room walls and installed working table in the room than the central one. It is also found that for different exhaust grille arrangements, the performance of the ventilation system in the horizontal symmetric case is higher than asymmetric and vertical symmetric ones. At the same time, it is observed that the variations of contaminant concentration in both Eulerian and Lagrangian approaches are almost the same. The results of the velocity and particle concentration show good agreement with the available experimental data in the literature. (C) 2016 Elsevier B.V. All rights reserved.