The urban measurement station of the team is at the roof of a building (at around 30 m above ground level) in the center of Patras, a city with 300,000 inhabitants. The building is one of the tallest in the city and the station provides measurements of the urban background. A PM2.5 sampler is located there and is used for routine measurements of the aerosol mass concentration and composition. Additional instruments (gas and aerosol) are added during intensive measurement periods. The station has been operating since 2009.