States that the quality of the air that enters a laboratory depends a great deal on the height of the stacks on top of the building and the location of the fresh air intakes relative to the stack location and the prevailing winds. If the exhaust and ventilation system are poorly designed, routine or accidental emissions from the stacks can be recirculated into the building. Presents an objective approach used to evaluate the effect of stack design on concentration levels at fresh-air intakes and pedestrian areas. The method examines local meteorology, expected chemical emissions, and their odour and health thresholds. Screening equations for estimating maximum concentrations are then employed. If thresholds are exceeded, wind tunnel measurements are then employed to refine concentration estimates and to improve the stack design. Presents examples of the methods.

KEYWORDS: Laboratories, outdoor air, supply air, flues, air inlets