Table 3.

Studies on the inter-flat airborne transmission of infection driven by combined buoyancy and wind effect.

Reference	Method	Study object	Main result	Related conclusion	Remark
Niu and Tung [26]	On-site tracer gas measurement (SF6 & CO2)	Two adjacent units on 1F and 2F at Wing Shui House in Hong Kong	Ona windless day the ratio of the SF6 concentration in the upper room to the lower room ranged from 2.9% to7%, depending on the locations, and the re-entry ratio was 4.8%; Outside wind speed, when increased from 0−0.03 to 2.48 m/s, could lower the maximum concentration ratio to 3.6% and re-entry ratio to 0.6%.	For the studied building configurations and an indoor/outdoor temperature difference of 3–5°C, the mass fraction is influenced by the temperature differences at the wind speed range of 0–0.07 m/s. While the turbulence effect ofa wind speed over0.9 m/s will overwhelm the thermal force.	Smoke visualization showed that the airflow along the façade was fairly turbulent and flow directions varied drastically. But most of the time, upward vertical airflow dominated, though downward or horizontal movement was occasionally observed.
Gao et al. [29]	CFD modeling (RNG k-ε model with CO2 asa tracer)	Two adjacent units on 2F and 3F ina slab-like building	For an indoor/outdoor temperature difference of5°C, the re-entry ratio was 7.5% ona windless day. As wind speed ascended from 0.5 to2.0 m/s, the re-entry ratio increased up to 16.3%. If the wind speed increased further to 4.0 m/s, the re-entry ratio was the lowest (3.5%).	For the studied case, a gentle wind forces the warm polluted plume to enter into the upper window by its horizontal momentum. But high-speed winds may function like an air curtain, suppressing the convective spread of pollutants between flats.	Only the transmission between two adjacent flats was discussed; Only wind normal to the window is taken into account; The finding still needs more experimental validations.
Zhang et al. [39]	CFD modeling (standard k-ε model)	A typical residential building witha cross floorplan	The HF (haze-fog) studies, where the pollutant density was adjusted to be heavier (+50%), same and lighter (−50%) than air, showed that the pathway of HF migration in the re-entrant area of the studied building for both windward and leeward discharge remain unchanged when compared with the case dominated by wind-structure interaction.	With the approaching wind speed at the building height (1 m) of3.27 m/s, the air pollutant dispersion around the building model is dominated by wind-structure interaction and buoyancy effect associated with the pollutant specific weight within the range tested only playsa minor role in the dispersion process.	Only the vertical air pollutant dispersion in the re-entry area of the specific building for the windward and leeward case was studied; The inter-flat transmission driven by the combined buoyancy and wind effect need further investigations.