An air filter unit for removing contaminations from air is disclosed. The air filter unit includes an airflow generating device configured to generate and direct at least one airflow from an air inlet to an air outlet, a filter disposed between the air inlet and the air outlet and including at least one filter layer for removing contaminations from the at least one airflow, a heater disposed upstream of the filter and configured to heat the at least one airflow directed towards the filter, an ejection device disposed upstream of the filter and configured to inject a sterilizing agent into the at least one airflow directed towards the filter, and a duct interposed between the air inlet and the filter and configured to feed the at least one airflow to the filter. The duct includes a volute-like outlet portion, and the ejection device is arranged in the duct.