For the disinfection of a room, a method and a device are proposed by which aqueous biocides with polymer-containing active substances are discharged, in the form of mist with a mean particle size of less than 10 μm, into a room by means of ultrasound technology. To be able to discharge the mist gently into the room in a way that saves energy, it is proposed that the aqueous polymer-containing biocide is firstly atomized on an ultrasound membrane, after which the atomized aqueous polymer-containing biocide is discharged into the room by at least one fan, with air as carrier medium.