Diffusional Particle Deposition in the Human Nose and Mouth

Abstract

Human nose and mouth serve as an effective filter for particles inhaled into the lung. For sufficiently small particles, particle loss to the wall surface of the air pathways is expected to be significant owing to the presence of strong Brownian diffusion. In this paper, we present the filtration results of ultrafine particles obtained from a simulation experiment in a cast of human oropharynx. It was found from the convective diffusion process that at normal breathing rate the inspiratory deposition efficiency of particles of diameter 0.001 μm in nose and mouth is 28.5% and 16.5%, respectively. These deposition fractions rapidly decrease to 0.1% and 0.05% for particles of diameter 0.1 μm.