An air intake channel (1) comprises a duct (3) of flexible material and has openings (7) in the upper half of the duct wall (5) for allowing fresh air to pass through. Inside the duct there is a winding shaft (9) which runs parallel to the longitudinal axis of the duct. This winding shaft is connected along a contact line to the inner wall of the duct. The wall (5) of the duct (3) is formed by a lightweight canvas which is maintained in spherical shape against the force of gravity as a result of overpressure in the air intake channel and can also be wound up on the winding shaft (9). By rotating the winding shaft (9) both the duct part (5A) located on one side of the winding shaft and the duct part (5B) located on the other side of the winding shaft is wound onto the winding shaft. As a result, a plurality of openings (7) in the duct wall are shut off.
