an aerosol generator for producing fine droplets in large quantities is used in an apparatus which can produce small particles having a high degree of crystallization and large surface area . the aerosol generator includes a chamber having a porous filter and a solution , and air is supplied to an upper side of the filter . a low pressure driving force , such as by a vacuum , is supplied to the chamber below the filter to generate droplets . a pyrogenetic reactor dries and pyrolyzes the droplets produced by the aerosol generator to give ultrafine particles and an ultrafine particle collector collects the ultrafine particles obtained by the pyrogenetic reactor . the low pressure driving force moves the droplets through the pyroletic reactor .