An oilsands developer requested to scope a potential increase in their facility sulphur dioxide (SO2) emission limit to allow for operational flexibility. To support this regulatory amendment request, Matrix Solutions Inc. conducted refined air dispersion modelling at the higher sulphur dioxide rate to predict air quality impacts of the change. The initial ground level sulphur dioxide concentration predictions were higher than expected under certain wind conditions. Matrix determined the problem was with the building shape and orientation of the steam generator stacks causing building downwash. Matrix worked with the client to redesign the building and orientation of emission sources to drastically reduce the predicted air quality impacts of the proposed change to sulphur dioxide emissions.