ABSTRACT
The deposition of aerosols in the human lung is primarily due to the mechanisms of inertial impaction, gravitational sedimentation, and Brownian diffusion. Inertial impaction causes most of the particles larger than 5 j.lrn to deposit in the upper airways. Brownian diffusion affects smaller particles «lj.lm), which deposit mainly in the alveolar region. Sedimentation is the gravitational settling of particles and mainly affects particles in the size range I to 8 j.lm. Of these three mechanisms, sedimentation is the only gravity-dependent process and is changed in altered gravity (G) environments.
