An air sterilizer unit having at least one inlet and at least one outlet comprising (a) a filter housing having an interior space (12,50) wherein at least one UVC light (24,74) 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, wherein the UVC light source is adapted to provide UVC light at 250-260 nm, wherein the at least one filter is a HEPA filter (18,78) capable of removing air borne particles having a diameter less than 0.5 μm, wherein a second filter (20,80) which is UVC resistant is located between the UVC light source and the at least one filter and comprises an active carbon filter capable of removing air borne particles having a diameter less than 100 μm, wherein a third filter (22,82) which is UVC resistant is located between the UVC light source and the second filter and is capable of removing air borne particles having a diameter less than 100 μm, wherein the filter is coated with TiO 2. (a) a filter housing having an interior space (12,50) wherein at least one UVC light (24,74) 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, wherein the UVC light source is adapted to provide UVC light at 250-260 nm, wherein the at least one filter is a HEPA filter (18,78) capable of removing air borne particles having a diameter less than 0.5 μm, wherein a second filter (20,80) which is UVC resistant is located between the UVC light source and the at least one filter and comprises an active carbon filter capable of removing air borne particles having a diameter less than 100 μm, wherein a third filter (22,82) which is UVC resistant is located between the UVC light source and the second filter and is capable of removing air borne particles having a diameter less than 100 μm, wherein the filter is coated with TiO 2. 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, wherein the UVC light source is adapted to provide UVC light at 250-260 nm, wherein the at least one filter is a HEPA filter (18,78) capable of removing air borne particles having a diameter less than 0.5 μm, wherein a second filter (20,80) which is UVC resistant is located between the UVC light source and the at least one filter and comprises an active carbon filter capable of removing air borne particles having a diameter less than 100 μm, wherein a third filter (22,82) which is UVC resistant is located between the UVC light source and the second filter and is capable of removing air borne particles having a diameter less than 100 μm, wherein the filter is coated with TiO 2.