Penetration of air-borne particulates through the human nose.

Five volunteers were exposed to aerosols of methylene blue, bismuth subcarbonate glycerol, sodium sulfate, and tyrosine. Aerosols were drawn through the nose at 17 liters/min. A plot of equivalent impaction diameter (aerodynamic unit density) against penetration shows good consistency for the various particles (importance of impaction). The hygroscopic aerosols (e.g., glycerol) showed lower penetration percentage at each particle size; this effect was significant but not large. Importance of nasal hairs was emphasized by experiments after clipping, which showed the percentage of total removal attributable to nasal hairs was up to 73% for larger particles and 2% for smaller particles.