Abstract: An air-supply device (1) for supplying breathing air into a breathing-air region (2) has at least one inflow opening (4, 6) for supplying breathing air, and also has an interior (10) and at least one outflow region (11), via which breathing air flows out into the breathing-air region (2). The inflow opening (4, 6) is connected to the outflow region (11) via the interior (10). The outflow region (11) is connected to the outflow region (11) via the interior (10). The outflow region (11) is formed on a flexible, air-permeable material (12). In order to provide for flexible use of the air-supply device (1) and to avoid any significant adverse effect to a user, provision is made for the air-supply device (1) to have a sheet-like, flexible portion (16), which has a first flat side (7) and a second flat side (8), located opposite the first. The outflow region (11) is arranged on the first flat side (7). The interior (10) is formed between the first flat side (7) and the second flat side (8).