In recent years, population exposure to air pollution has been a major concern. Indoor air quality (IAQ) is mainly monitored with CO2-concentration-based indicators. High levels of CO2-concentration are avoided in buildings when airing by the windows is done and/or when air exchange rate of the existing ventilation is regulated, based on a CO2-level-information. However, as contributing to maintain low CO2-concentration-levels indoors, the increase of outdoor air intake is associated with a more or less important introduction of outdoor air pollutants in the building. Among these pollutants, there are particulate pollutants as PM2.5 and there is NO2 that is a gaseous pollutant mainly emitted by the road-traffic. Many previous papers dealt with the indoor/outdoor dynamics. However, only rare studies, like Bucur et Danet (2019), Bi et al. (2021) or Nezis et al. (2022), were based on outdoor air measurements up to 500 m away from the studied buildings. The aim of this study is to evaluate such dynamics for PM2.5 and NO2. It was based on a twomonths measurements campaign in three buildings presenting different ventilation types. In addition to the reference data of the local air quality monitoring station, an optical particles measurement was introduced on the façade of the buildings.