This article reports airflow, particle transport, and pressure differential control of a front-opening unified pod/load port unit (FOUP/LPU) minienvironment system using both experimental and computational fluid dynamics (CFD) approaches. The stochastic tracking approach in the Discrete Phase Model of Fluent software was adopted to predict particle trajectory. The predicted velocity vectors were verified by experimental ones, which were measured by a 3D ultrasonic anemometer. Particles from the upper edge of the FOUP produce a greater contamination risk than those from the lower edge of the FOUP. Particles generated on the moving part of the LPU can be entrained to the back surface of wafer in the bottom position. The parameters that affect the pressure differential between the minienvironment and surrounding environment were analyzed. The minimum pressure differential required to prevent particles from ingression to the minienvironment was determined.