The present invention relates to air sterilizer unit having at least one inlet and at least one outlet comprising (a) a filter housing having an interior space wherein at least one UCV light source adapted for radiating microorganisms, is located, and at least one filter with a capacity to reduce or remove microorganisms from ambient air, wherein the filter is UVC resistant and is located between the UVC light source and the at least one outlet, (b) an air transportation unit, wherein the air transportation unit is adapted to move ambient air from the at least one inlet into the filter housing, and being exposed to the UVC light and through the at least one filter, and through the at least one outlet.