A photocatalytic reactor (100) for use in a heating, ventilation and/or air conditioning system. The system comprises a longitudinal housing (110) having a wall (112) and allowing air or gas to pass through along the longitudinal direction of the longitudinal housing (110). The system also comprises a plurality of tubes (120) positioned in the longitudinal housing (110) and arranged such that some outer tubes (120a) are positioned closer to the housing wall than some inner tubes (120b). The tubes (120) have their longitudinal axis parallel with the longitudinal axis of the longitudinal housing (110) allowing said air or gas to pass along and through said tubes (120) and the tubes (120) furthermore comprise photocatalytic material in or on their tube walls. The system also comprises an irradiation system (130) for irradiating the photocatalytic material for inducing catalytic action. The irradiation system (130) and plurality of tubes (120) are configured so that upon irradiating by the irradiation system (130) photocatalytic material of said outer tubes (120a) as well as of said inner tubes (120b) is irradiated.La présente invention concerne un réacteur photocatalytique (100) destiné à être utilisé dans un système de chauffage, ventilation et/ou climatisation. Le système comprend un logement longitudinal (110) ayant une paroi (112) et permettant à de l'air ou à du gaz de passer au travers le long de la direction longitudinale du logement longitudinal (110). Le système comprend également une pluralité de tubes (120) positionnés dans le logement longitudinal (110) et agencés de telle sorte que certains tubes externes (120a) sont positionnés plus près de la paroi du logement que certains tubes internes (120b). Les tubes (120) présentent un axe longitudinal parallèle à l'axe longitudinal du logement longitudinal (110) permettant audit air ou gaz de passer le long desdits tubes (120) et à travers ceux-ci, et les tubes (120) comprennent en outre un matériau photocatalytiq
