We propose to solve two important engineering design challenges associated to the optimal placement of jet fans in a car park, by means of CFD. Given a proposed arrangement of jet fans, we provide a simulation framework for rigorous identification of those fan units (if any) that do not contribute to improving the overall air quality in the enclosure. Based on this statistical analysis, we then solve the following constrained optimization problem: Given maximum fan capacities and an air quality level requirement, establish a minimum-cost fan configuration which meets it for the car park in question. The proposed optimization framework is illustrated by an example from an actual car park.