An airbag unit comprising an airbag which is fillable with a gas in order to protect a vehicle occupant is provided. The airbag comprises two material layers which are connected to each other at their circumferential edge by means of a connection, wherein the connection is interrupted at least in one portion, in order to form an outflow opening, via which gas can escape from the airbag during the filling and/or after the filling, at least one covering device for covering the outflow opening, wherein the covering device comprises at least one closure element which is arranged moveably in relation to the outflow opening in order to vary the size of the outflow opening, and a control unit which is designed to move the at least one closure element in relation to the outflow opening in such a manner that the outflow opening is opened up, covered or partially covered.