The paper discusses a menu-driven ventilation model for a personal computer (PC), developed to determine the distributions of time-averaged flow fields and particulate or gaseous contaminants under isothermal conditions and for a given effective turbulent diffusion coefficient. The model was written for a PC so that engineers can use it as a tool to evaluate a potential ventilation performance in indoor space yet to be designed. The model's computational speed is extremely fast (a few minutes) with reasonable accuracy. This paper discusses the computational algorithm and user interactiveness for the use of this model. Case studies were performed for a simple indoor environment. Ventilation effectiveness in relation to the locations of the supply air duct and the contaminant source was investigated.