IRSST - Institut de recherche Robert-Sauvé en santé et en sécurité du travail

Tracer-gas studies of the recirculation of exhaust air in urban buildings


Under certain atmospheric conditions, a significant fraction of toxic building-exhaust emissions may be captured by the fresh-air intakes of the same building or adjacent ones and recirculated, creating a health risk for building occupants. This problem is particularly acute in industrial and institutional laboratories. Determination of the minimum safe distance between exhausts and fresh-air intakes in urban settings is a complex exercise that must take into account many parameters. The primary objectives of this tracer-gas field study were to evaluate the minimum-dilution models suggested by the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) and to determine the reliability of wind-tunnel simulations. One of the ASHRAE models was found to be most applicable to situations involving toxic gases, while two others were better suited to situations involving foul-smelling gases. For buildings with complex geometries, wind-tunnel models are preferable to the ASHRAE models.

Additional Information

Type: Project
Number: 0095-2150
Status: Completed
Year of completion: 2005
  • Louis Lazure (IRSST)
  • Ted Stathopoulos (Université Concordia)
  • Patrick Saathoff (Université Concordia)