Measurement of aerosol deposition in a mouth-throat model by laser diffractometry in the presence of air and other carrier gases

This work describes the development of an experimental setup that allows rapid determination of deposition characteristics of aerosols in different carrier gases and different geometries, based on particle size distribution measurements using the laser diffraction method. Isotonic saline solution was nebulized by a vibrating mesh nebulizer. The aerosol was introduced to a humidified gas stream of air or helium-oxygen. The particle size distributions at the inlet and outlet of a mouth-throat model were measured by laser diffractometry. Additionally, the nebulizer output and the deposition mass in the model were determined gravimetrically. The deposited percentage of the nebulizer output was highest in air. The laser diffractometry data showed increasing deposition of larger particles; in the given model particles larger than 9 mum in diameter deposited completely. Compared to the entering particle size distribution, however, the mass fraction in small particles was increased in the distribution leaving the model. The developed setup can be used for a rapid determination of deposition characteristics in different geometries and different gases. The shift towards small particles should be investigated further. Particle shrinkage via evaporation could be one of the reasons despite the humidification of the carrier gas.