This study is concerned with three-dimensional air flow field for improving the ventilation performance of a minienvironment in which toxic gas is produced during the coating process. To investigate the air flow field, measurement for the velocity distribution has been made by using a three-dimensional ultrasonic anemometer, and numerical simulation using computational fluid dynamics (CFD) analysis tool has also been performed. Results of the numerical simulation based on the RNG k-epsilon turbulence model are confirmed by the experiments, and modifications in geometric configuration of the system are investigated. It is found that the numerical and experimental approaches used in this study lead to useful information of flow field and the ventilation performance in the minienvironment may be greatly improved by adjusting the location of the HEPA and modifying the shape of the inlet of the exhaust pipe. (c) 2004 Elsevier B.V All rights reserved.