Low pressure chemical vapor deposition (LPCVD) processes are used in the microelectronic manufacturing industry. As circuit dimensions decrease, it becomes ever more critical to control the particulate contamination of the wafer during fabrication. To accurately predict the particle motion, and thus minimize contamination, the flow field must be known. This paper outlines the procedure to numerically simulate the velocity, temperature, and concentration fields in a low pressure application. From these solutions, accurate particle trajectories are predicted using a Lagrangian formulation that includes effects of temperature, drag, gravity, and Brownian motion.