Device for mixing two air flows

The device has first and second air channels (104, 106) guiding first and second air streams, and third air channel (108) receiving first air stream from outlet ports of the first and second air channels. A lamella arrangement (110) includes lamellas e.g. rigid strips, that are arranged at various distances adjacent to each other, where the lamellas are extended in a transition region between the outlet ports in the air channels. The lamellas are extended based on a threshold region between the first and second air channels in the third air channel.