A CFD-based parametric study was carried out for a prototype general exhaust system widely used for ventilation and control of diesel exhaust in large enclosed locomotive facilities. The parameters of fan flow rate, ceiling height, fan spacing, and locomotive position relative to the fan were varied between two values representing the low and high ends of their expected ranges. A set of simulations was set up using factorial experimental theory, which allows variables and interactions having a significant effect on an outcome to be identified. Two outcome variables were considered: the maxi-mum time-averaged concentrations at the breathing plane for occupants standing on the floor and on a platform. Regression was then used to obtain an equation to predict these maximum concentrations as a function of the independent parameters. Using these equations, a design procedure that could be used by designers to maintain a target concentration limit for a crit-ical contaminant has been developed and demonstrated.