US 6129080 A abstract an atomizer for dispensing a powder or liquid product which is atomized by a stream of compressed air and further has either means to prevent or stop the product from atomizing in response to a positive pressure in the atomizer or a secondary reservoir located between the product reservoir and a product outlet from which the product is atomized said secondary reservoir is in fluid connection with a second chamber the second chamber being operable in response to a positive pressure in the atomizer to drive fluid from the secondary reservoir application_number US 1372798 A description in embodiments of the invention it is preferred that the apparatus is one which generates atomized product when the pressure in the apparatus is atmospheric or less than atmospheric i e negative but that atomisation is prevented or stopped when the pressure in the apparatus is positive i e greater than atmospheric in embodiments of the invention the nebulizer may dose the medicament to the user via a mouthpiece though it is envisaged that atomized medicament could be dosed to the user through a sealing face mask the invention is further described by way of example only with reference to the accompanying drawings in which fig1 shows a schematic cross section of an embodiment of the invention in use with the user inhaling fig2 shows a schematic cross section of the embodiment of fig1 in use with the.