Objective: Due to the airborne transmission of the Coronavirus Disease (Covid-19) via aerosols, we investigated the effect of a mobile air filter system in a surgical examination room. Methods: A mobile indoor air cleaner (AP 90, DEMA-airtech, Germany) was run during regular surgical consulting hour in our outpatient’s clinic. Aerosol concentration was measured by Fidas Frog fine dust monitoring system (Palas, Germany) by constantly recording PM1.0, PM2.5, PM4, PM10 and the total particle load PMtot. Results: The use of the air filter system led to a significant reduction of aerosols in the room despite the fact that there were various numbers of persons in the room constantly. Conclusion: The use of a high efficiency air filtration device, especially in examination rooms with poor ventilation, e.g., lack of windows or local exhaust is recommendable.