peer reviewed ; In 2020, the world was affected by an unprecedented health crisis. Europe had to close its internal and external borders, and the majority of countries had to impose lockdowns on their people. Shops, restaurants, building sites, and industries had to close, and working from home became the rule. This paper reflects a study conducted from 17 March to 25 June 2020, in which homemade low-cost devices measured PM2.5 concentrations at three different locations around a Belgian school and background concentrations. The period monitored covered seven reopening stages from lockdown to the reopening of borders. The overall analysis did not show any correlation between traffic and PM2.5 concentrations in the streets in any of the phases. However, the analysis of each reopening showed that it was possible to observe significant differences in the background concentrations measured in a rural town and on urban streets.