An air supply system (200, 300) for providing a clean air flow (250) in a room (1) is provided. The air supply system (200, 300) comprises a first air supply section (120) through which a first flow of clean air is supplied with a lower temperature than the temperature of the ambient air in the room (1), and a second air supply section (230) through which a second flow of clean air is supplied. The first air supply section (120) is arranged to form a gravitationally induced downward flow, whereas the second air supply section (230) is arranged to adjust the velocity (v 1 ) of the second flow of clean air when entering the second air supply section (230) to a predetermined velocity (v 2 ), and is adapted to direct the second flow of clean air downwards. A method (600) for providing a clean air flow in a room is further provided.
