Inspiratory deposition of ultrafine particles in human nasal replicate cast

Abstract The deposition of particles in replicate cast models of the human nasal cavity has been measured in three different laboratories for a range of particle sizes from 0.6 to 200 nm. The results of these measurements on four different casts can be fit by a single equation of the form η=1 − exp [−bQ − 1 8 D 1 2 ], where η is the fraction of particles deposited in the nasal cavity, Q is the volumetric flow rate (1 min −1 ), D is the particle diffusion coefficient (cm 2 s −1 ), and b is found to be 12.65 ± 0.17. The measurements were conducted over a range of flow rates from 1.4 to 28.71 min −1 (501 min −1 for sizes from 4.6 to 200 nm) using radon and thoron decay product aerosols as well as larger ultrafine particles. These results thus represent a current best estimate of the diffusional deposition of ultrafine particles in the human nasal cavity.