Indoor-outdoor pollutant concentration modelling: a comprehensive urban air quality and exposure assessment

This paper is devoted to the investigation of the relationship between concentrations of traffic-related pollutants at pedestrian level in the street and indoor pollutant concentrations inside different rooms of different floors of a standard building. CFD modelling covering the whole urban environment, including the interior of a target building, is used to explicitly simulate wind flow and pollutant dispersion outdoors and indoors. A wide range of scenarios considering different percentage and location of open windows and different wind directions is investigated. A large variability of indoor pollutant concentrations is found depending on the floor and configuration of the open/closed windows, as well as the wind direction and its incidence angle. In general, indoor pollutant concentrations decrease with floor, but this decrease is different depending on the scenario and the room investigated. For some conditions, indoor concentrations higher than the spatially averaged values in the street (up to a ratio of 1.4) are found in some rooms due to the high pollutant concentrations close to open windows. This behavior may lead, on average, to higher exposure inside the room than outside although, in general, indoor pollutant concentrations are lower than that found in the street at pedestrian level. Results are averaged for all scenarios and rooms being the average ratio between indoor and oudoor concentrations 0.56 +/- 0.24, which is in accordance with previous studies in real buildings. This paper opens to a unified approach for the assessment of air quality of the total indoor and outdoor environment.

Automated summary

This paper investigates the relationship between traffic-related pollutant concentrations at pedestrian level and indoor pollutant concentrations in different rooms of a standard building. Through CFD modelling, the study simulates wind flow and pollutant dispersion both outdoors and indoors. The results show that indoor pollutant concentrations vary significantly depending on the floor, window configuration, wind direction, and incidence angle. Generally, indoor concentrations decrease with floor, but the extent of decrease varies across scenarios and rooms. Indoor concentrations higher than the street average are found in some rooms due to high pollutant concentrations near open windows. However, on average, indoor concentrations are lower than those at pedestrian level. The average ratio between indoor and outdoor concentrations is 0.56 +/- 0.24, consistent with previous studies. This paper provides a unified approach for assessing air quality in indoor and outdoor environments.