Disclosed is a flow device for an additive manufacturing device. The device includes a gas supply line located outside the process chamber to conduct gas to a gas inlet. The gas supply line includes a first line section extending in a first extension direction and a maximum width that extends transverse to the first extension direction and parallel to the build area. A length of the first line section is at least half as large as the maximum value of the width. The first line section also includes a first subsection spaced from the gas inlet and including a first flow conditioning unit and a wall of the first line section. The first flow conditioning unit substantially aligns the gas stream in the first extension direction.