We have utilized Computational Fluid Dynamics (CFD) Modeling for over 15 years to model air and particle flow within building spaces, and in exterior applications around buildings. This tool has proven to be very effective in evaluating HVAC system options and predicting performance early in the design process. It can also effectively identify wind flow patterns around buildings which enables us to avoid potential re-entrainment of fumes or smoke into building air intake openings, providing a healthier indoor environment.