AEROSOLIZATION OF PARTICLES FROM A BUBBLING LIQUID - CHARACTERISTICS AND GENERATOR DEVELOPMENT

A new aerosol generator is introduced in which particles suspended in a liquid are aerosolized by gentle bubble bursting. Tangential injecti on of dry air to the bubbling surface dries the airborne droplets imme diately after aerosolization so that they rapidly shrink in size and a re carried out from the generator by inward and upward swirling air mo tion. The new generator has been evaluated with monodisperse PSL parti cles in the size range of 0.73-5.1 mu m and with a saline solution usi ng a time-of-flight aerodynamic particle size spectrometer (Aerosizer) . It was found that, in contrast to pneumatic nebulization (e.g., with a Collison nebulizer), the new generator's output in undesirable liqu id droplets is very small, while its output in dry PSL particles is hi gh. When using the new aerosol generator, a minimum number of the nebu lized droplets is returned to the liquid pool, thus optimizing the num ber of particles available as test aerosols. The aerosol concentration was found to be constant and stable for at least 30 min with the prot otype generator tested. It is shown that the relative humidity of the effluent flow can be regulated. For microorganisms aerosolized by this generator, the shear stress is expected to be considerably lower than in conventional aerosol generators. (C) 1997 American Association for Aerosol Research.