Inter-unit transmission of pollutants in naturally ventilated buildings adjoining a street canyon: a parametric study

The recent pandemic has accentuated the importance of clean indoor air and the risks associated with the airborne spread of pathogens. Outdoor meteorology and building configuration can spread pollutants and pathogens between different indoor units, deteriorating the air quality in the process. While previous studies have mainly focused on inter-unit pollutant crossflow in highrise buildings and isolated scenarios, the role of street canyon configurations in urban areas remains crucial for understanding ventilation characteristics and limiting the spread of contaminants. This research aims to evaluate the wind-driven transmission characteristics of pollutants between adjacent indoor units situated along a street canyon. By employing a numerical model, validated against experimental data, the study compares the impacts of five building ventilation strategies, each representing specific window opening combinations on the two buildings. Based on the environmental conditions set for the study, the results demonstrate that inter-unit transmission is reliant on both, the air change rate and the unit’s specific location. By increasing the air change rate, cross-transmission decreases, offering an effective strategy to limit contaminants. However, units placed at the centre of the street canyon are more susceptible to contamination, requiring additional precautions for their occupants. Notably, the spatial arrangement of apartments (or units) within the canyon influences pollution diffusion along the street. Apartments at the canyon's edges may not directly contaminate units further down the street, but they still have a subtle influence, contributing small doses of pollutants. This study advances our understanding of inter-unit pollutant transmission in urban street canyons. Armed with these insights, residents can make informed decisions about adopting tailored ventilation strategies based on their apartment's location, proactively safeguarding their health. By employing the right ventilation strategies, residents can effectively minimize exposure to airborne pollutants, ensuring a healthier living environment in densely populated urban areas.