A device has a freely rotatable rotor (13), which is equipped at its circumference with multiple nozzle heads (14). The rotor (13) is arranged above a row of preforms (1), wherein these preforms (1) are moved onto feed rails (7, 8) in conveying direction (9). At least one of the nozzle heads (14) respectively immerses into the hollow space (11) of a preform (1) and is taken along by the latter in conveying direction (9). During the immersion, a gas stream is blown into the hollow space (11) of the preform (1) by a nozzle (16) in the nozzle head (14).