A Study of airflow and particle transport in two types of clean room is presented. The study investigates the flowfield and contaminant particle transport in mixed flow and Vertical Laminar Flow (VLF) cleanrooms. The study consisted of modeling and evaluating the effect of using perforated or raised floors in combination with clean hoods. The considered air velocities in the room were 20, 30 and 50 feet/min. Contaminant particle sizes considered were 0.5 and 5 microns. The particles were injected at six different locations in the room. A simulation of a mixed flow clean room with side return (without raised floors) is also enclosed for comparison. Artistic impressions of flow visualization of the flow is also presented for comparison.