Filter unit (1) and use of the same, for treating a main through flow (14) of air, said filter unit (1) comprising a main inlet (15) and a main outlet (16) in fluid connection and arranged at a distance from each other, at least one ultraviolet light source (3) adapted for air treatment arranged between the main inlet (15) and the main outlet (16) at least one electrical component (13) for operating the ultraviolet light source (3). The main flow (14), when the filter unit (1) is in use, creates a negative pressure inside the filter unit (1) between the main inlet (15) and the main outlet (16). The filter unit (1) further comprises a compartment (4), separated from the main flow (14), in which compartment (4) the at least one electrical component (13) is arranged. The compartment (4) is provided with a secondary outlet (12) in fluid connection with the main flow (14) and further provided with a secondary inlet (11) in fluid connection to an outside of the filter unit (1) so that a secondary flow (10) from the secondary inlet (11) through said compartment (4) to the secondary outlet (12) is controlled by the negative pressure inside the filter unit (1) when in use.Linvention porte sur une unité filtrante (1) et sur son utilisation pour traiter un flux dair traversant principal (14), ladite unité filtrante (1) comprenant une entrée principale (15) et une sortie principale (16) reliées fluidiquement et disposées à une certaine distance lune de lautre, au moins une source de lumière ultraviolette (3) apte à traiter lair et disposée entre lentrée principale (4) et la sortie principale (16) au moins un composant électrique (13) destiné à commander la source de lumière ultraviolette (3). Lorsque lunité filtrante (1) est en utilisation, le flux principal (14) crée une pression négative à lintérieur de lunité filtrante (1) entre lentrée principale (15) et la sortie principale (16). Lunité filtrante (1) comprend en outre un compartiment (4) séparé du flux principal (14), dans
