The invention relates to a device for controlling and guiding gas flow in atomizers, in breathing and rebreathing regions of a respiratory appliance. A first embodiment comprises a bypass device; and a said second embodiment comprises a valve which is timed by the respiratory appliance, such that the dead space is not filled with aerosol. Both embodiments provide for an application of aerosol only in the inspiration phase, reduction of the applied medication quantity by reducing the atomization of the dead space, reduction of the side effects of the medications, and sufficient moisturizing of the airways.