The aqueous suspension to be aerosolised (aerosol substance) is dispersed by a one-substance nozzle within the aerosol formation chamber of the ATM 240/S. The supplied liquid flow disintegrates and forms a broad distributed (polydisperse) droplet aerosol (primary aerosol). Due to inertia and gravitational settling, too large droplets leave immediately the primary aerosol after generation. A dry purge air flow, which is fed into the aerosol formation chamber, transports the remaining airborne droplets into the dip tube and initiates contemporaneous the process of droplet drying. To ensure a drying stable test aerosol, the aerosol passes prior leaving the generator an implemented drying section.