A vehicle, in particular a railway vehicle, comprising: - an upper room and a lower room respectively for travellers, - at least one side wall comprising at least one first area located in the upper room, and at least one second area located in the lower room, - a floor of the upper room defining at least one stairwell adjacent to the side wall in a transverse direction substantially parallel to the floor, - at least one staircase for the passage of passengers between the lower hall and the upper hall via the stairwell, characterised in that the vehicle comprises: - a ventilation system adapted to create at least a first downward air flow along the first area, and at least a second upward air flow along the second area, and - at least one trim member fixed to the side wall between the first area and the second area along a direction of elevation substantially perpendicular to the floor, the trim member projecting transversely with respect to the first area and the second area, the trim member defining a first guide surface adapted to deflect the first air flow and form a third air flow located above the floor and oriented substantially transversely, the trim member defining a second guide surface configured to deflect the second air flow and form a fourth air flow located below the floor and oriented substantially transversely. - an upper room and a lower room respectively for travellers, - at least one side wall comprising at least one first area located in the upper room, and at least one second area located in the lower room, - a floor of the upper room defining at least one stairwell adjacent to the side wall in a transverse direction substantially parallel to the floor, - at least one staircase for the passage of passengers between the lower hall and the upper hall via the stairwell, characterised in that the vehicle comprises: - a ventilation system adapted to create at least a first downward air flow along the first area, and at least a second upward air flow along the second area, and - at least one trim member fixed to the side wall between the first area and the second area along a direction of elevation substantially perpendicular to the floor, the trim member projecting transversely with respect to the first area and the second area, the trim member defining a first guide surface adapted to deflect the first air flow and form a third air flow located above the floor and oriented substantially transversely, the trim member defining a second guide surface configured to deflect the second air flow and form a fourth air flow located below the floor and oriented substantially transversely. - a ventilation system adapted to create at least a first downward air flow along the first area, and at least a second upward air flow along the second area, and - at least one trim member fixed to the side wall between the first area and the second area along a direction of elevation substantially perpendicular to the floor, the trim member projecting transversely with respect to the first area and the second area, the trim member defining a first guide surface adapted to deflect the first air flow and form a third air flow located above the floor and oriented substantially transversely, the trim member defining a second guide surface configured to deflect the second air flow and form a fourth air flow located below the floor and oriented substantially transversely.