The invention relates to a device for diffusing air (1) inside a room, notably a breeding room. This device is noteworthy in that it comprises: - a cylindrical body (2), the upper part of which constitutes an air inlet and the lower part (22) of which comprises at least one air diffusion window (221) provided with fins (229a, 229b, 229c) with different inclinations, - and a shut-off member (3) comprising a cylindrical peripheral wall (31) and a central shut-off disc (32), in that said shut-off member (3) is able to move in the lower part of said body between a rest position, in which its peripheral wall (31) is located next to said diffusion window (221) so as to prevent the circulation of air, and a diffusion position, in which its peripheral wall (31) is no longer located next to said window so as to allow the circulation of air, and in that the movement between the rest position and the diffusion position takes place counter to the weight force of a counterweight, in the event of low pressure at the lower
