The invention provides a free standing treatment device for a dishwasher, the device comprising a. housing (I) containing a battery (10), a reservoir (5) of liquid, a transducer (8) arranged to receive power from the battery (10), the transducer (8) being operable to generate a mist of the liquid droplets which are ejected from an outlet in the housing (1). The device allows for the dosing of treatment compositions directly and automatically into the dishwasher.