Stratospheric ozone is proved to be vital for life on Earth, whereas tropospheric ground-level ozone represents a serious threat to both plants and animals, including humans. Assessing its impacts requires comprehensive monitoring. Only 25% of the Earth’s surface has ground-based data; leaving large spatial gaps. Exposure, however, is not purely outdoor: ozone penetrates indoors and reacts with indoor pollutants, reshaping what people actually breathe. Capturing both outdoor burdens and indoor penetration is therefore essential. The aim of this work is to measure ozone levels in the summer period in both indoor and outdoor environments in the Turin area using Monica low-cost sensors.