Abstract: Method and apparatus for an aerosol chamber having an input opening and an output opening with back pressure created in the chamber by an apertured barrier, such as a disk having a plurality of concentric and circumferentially disposed sets of openings to reduce the size of particles applied at the input opening before leaving the output opening, which is of lesser diameter than the input opening and extends to the input opening by an arcuate surface of revolution that serves to redirect interiorally of the chamber aerosol particles that have entered the chamber and reached the surface of revolution.