Abstract: A device for generating an air wall comprises a primary blower slit for generating a flat primary air stream in a passage opening mutually separating two spaces with different temperatures. Two adjacent air streams with the same direction and speed are added to the primary air stream. The primary air stream has a temperature between those of the secondary air streams. The absolute humidity of the air of the primary air stream is at least equal to that of the cold secondary air stream and lower than that of the warm secondary air stream. The air speed of the primary air stream amounts to at least 15 m/s. The width of the primary blower slit lies in the range of 15-40 mm. The length of the primary blower slit in the direction of the air stream lies roughly in the range of 5-40 cm, preferably 10-30 cm.