Carbon dioxide (CO₂) is a very important atmospheric pollutant, and to better understand the gas's source and sink dynamics, a mid-cost sensor network hosting 26 sites was deployed in and around Zurich, Switzerland. The sensor measurement performance was quantified, and natural and anthropogenic CO₂ emission sources were explored with a focus on what drives high CO₂ levels. The observations will be used further by others to validate what is thought to be known about CO₂ emissions in the region.