PURPOSE: To urge an exchange by automatically announcing the clogging of a bacterium removing filter to an operator when this filter is clogged.

CONSTITUTION: A liquid drug Lb for treatment is atomized by the energy of an ultrasonic transducer vibrator 8 and the atomized liquid drug ML is sent to a patient by using the air taken in via the bacterium removing filter 26 by an air pump 30. The bacterium removing filter 26 and the air pump 30 are communicated and connected with and to each other by a duct 28 of a hermetic type. A pressure sensor 30 for detecting the internal pressure of the duct 28 is provided in this duct. A clogging alarm device 38 is operated when the voltage detected by the pressure sensor 34 falls to a prescribed value or below.