The device comprises a supply container closed on all sides whereby only so much fluid flows out through the opening (3) in the partition wall (2) as a result of the underpressure and into the dosing chamber (4) until the fluid closes the opening. A constant fluid level (8) is set in the dosing chamber independently of the fluid level (7) in the supply container. Owing to the capillary action of the wick (11) after overcoming the partition the fluid (10) reaches the lower vaporisation chamber (5). The size of the fluid stream is determined independently of atmospheric influences by the dimensions and porosity of the wick and height difference between the two fluid levels. The fluid entering the vaporisation chamber is sucked up by the vaporisation element which has no direct contact with the wick.
