The use of UV-C air purification devices has gained attention due to the SARS-COV-2 pandemic, as the antiviral efficacy of UV-C radiation is well known and extensively studied. However, irradiation of air with UV-C radiation, in addition to inactivating viruses, also degrades photolabile substances such as aldehydes, nitrogen dioxide, or ozone and forms secondary products in the gas as well as aerosol phase. The simultaneous irradiation of TiO2 coated surfaces with UV-C radiation causes further surface-active processes, which enable additional degradation and formation pathways of trace substances and radicals. In the first part of the study, published here, we quantify the UV-C dose of the youvee® air cleaning device. The whole study including the results on the impact on common air pollutants like aldehydes, nitric oxides and ozone and their formed byproducts will be published open access in a peer reviewed journal.