The airborne transmission of infection between flats in high-rise residential buildings: Tracer gas simulation

N. P. Gao, Jianlei Niu, M. Perino, P. Heiselberg

Research output: Journal article publicationJournal articleAcademic researchpeer-review

142 Citations (Scopus)


Airborne transmission of infectious respiratory diseases in indoor environments has drawn our attention for decades, and this issue is revitalized with the outbreak of severe acute respiratory syndrome (SARS). One of the concerns is that there may be multiple transmission routes across households in high-rise residential buildings, one of which is the natural ventilative airflow through open windows between flats, caused by buoyancy effects. Our early on-site measurement using tracer gases confirmed qualitatively and quantitatively that the re-entry of the exhaust-polluted air from the window of the lower floor into the adjacent upper floor is a fact. This study presents the modeling of this cascade effect using computational fluid dynamics (CFD) technique. It is found that the presence of the pollutants generated in the lower floor is generally lower in the immediate upper floor by two orders of magnitude, but the risk of infection calculated by the Wells-Riley equation is only around one order of magnitude lower. It is found that, with single-side open-window conditions, wind blowing perpendicularly to the building may either reinforce or suppress the upward transport, depending on the wind speed. High-speed winds can restrain the convective transfer of heat and mass between flats, functioning like an air curtain. Despite the complexities of the air flow involved, it is clear that this transmission route should be taken into account in infection control.
Original languageEnglish
Pages (from-to)1805-1817
Number of pages13
JournalBuilding and Environment
Issue number11
Publication statusPublished - 1 Nov 2008


  • Airborne transmission
  • Cascade effect
  • Computational fluid dynamics (CFD)
  • High-rise residential buildings
  • Tracer gas

ASJC Scopus subject areas

  • Environmental Engineering
  • Geography, Planning and Development
  • Civil and Structural Engineering
  • Building and Construction


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