There is described an air filter unit (1) for removing contaminations from air comprising:- airflow generating means (22) configured to generate and direct at least one airflow (F) from an air inlet (4) to an air outlet (5)- filter means (15, 16) disposed between the air inlet (4) and the air outlet (5) and including at least one filter layer (15) for removing contaminations from the airflow (F)- heating means (8) disposed upstream of the filter means (15, 16) and adapted to heat the airflow (F) directed towards the filter means (15, 16)- ejection means (9) disposed upstream of the filter means (15, 16) and adapted to inject a vaporized, gaseous or liquid sterilizing agent into the airflow (F) directed towards said filter means (15, 16) and- a duct (25) interposed between the air inlet (4) and the filter means (15) and adapted to feed the airflow (F) to the filter means (15, 16)wherein the duct (25) comprises at least a volute-like outlet portion (26) for conveying the airflow (F) to the filter means (15, 16) and wherein the ejection means (9) are arranged in the duct (25).
