An air intake's location on the roof of a building is a determining factor for indoor air quality due to the possible reintroduction of contamination from the neighboring exhaust stacks. Ventilation system designers currently use tools such as mathematical models and wind tunnel simulations to estimate the dilution between the source and the air intake. These techniques are valid but do not take into consideration several variables, and sometimes the estimated dilution values differ from the measured values. Using field tests and boundary layer wind tunnel modeling, the authors studied the dilution phenomenon and impact of certain parameters (wind direction, stack height and location, roof irregularities, turbulence, air exhaust velocity) to refine the models used. This project has resulted in the development of guidelines intended for ventilation engineers. The results are also of interest to several professional associations and standardization organizations.
