The anatomical form of the nasal passage and the resultant air flow through it assures conditioning of inspired air, effective filtration of inhaled particles, and absorption of foreign gases. Nasal mucus flow transports deposited materials through the nose at a rate of about 5 mm/min; but in some normal subjects, rates are far lower than this. Nasal mucociliary transport is unaffected by the relative humidity of the inspired air.
Proctor DF, Andersen I, Lundqvist G. Clearance of Inhaled Particles From the Human Nose. Arch Intern Med. 1973;131(1):132-139. doi:10.1001/archinte.1973.00320070128014