Human respiratory tract deposition, mechanism

If inspired particles were carried only convectively with the bulk of airflow, losses of these particles in the respiratory tract would be negligible. However, all inspired particles experience a nonzero chance of being lost. This is due to particle transport toward airway and airspace surfaces as a result of mechanical and electrical forces acting upon the particles. Upon contact with these surfaces, the particles are deposited. The human respiratory tract can therefore be considered as an aerosol filter, removing particles from the inspired air. The effectiveness of this filter depends on... 

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