Despite the complexities of the air flow involved, it is clear that this transmission route should be taken into account in infection control.Ī thermal diffusivity (m 2/s) A window opening area (m 2) C number of new cases C d discharge coefficient c p specific heat of air (J/kg K) C 0 initial indoor tracer gas concentration (ppm) C τ tracer gas concentration at time τ (ppm) D depth of the room (m) e base of natural logarithms Fr Froude number g gravity acceleration (m/s 2) g′ reduced gravity to describe buoyancy force, g′= g High-speed winds can restrain the convective transfer of heat and mass between flats, functioning like an air curtain. ![]() 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. ![]() 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. This study presents the modeling of this cascade effect using computational fluid dynamics (CFD) technique. 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. ![]() 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. 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).
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