IES Consulting used CFD to model the release of potentially toxic fumigants from high level flue stacks and study the spread under different wind conditions to discover if they could potentially entrain into the intakes of nearby building air handling units. The BDH houses laboratories containing fume cupboards and fumigants are released during their purging process. IES also modelled the surrounding site to capture the effects they may have on air movement. A series of wind speeds and directions were modelled to ascertain a complete understanding of the air movement and fume distribution. Several configurations of the flue stacks were tested as part of this analysis to select the best performing strategy.