The present invention relates to a suction device (103) for a hood (101), comprising a motor, and further comprising an impeller driven by the motor and configured to draw an air flow and direct it into an outflow collar (203); the suction device (103) further comprises at least one flap (204, 205) connected to the collar (203) and hinged (301) on one side only, the at least one flap (204, 205) being configured to close the collar (203) when the impeller is idle, and to be lifted by the air flow so as to clear the collar (203) when the impeller is rotating.