It is widely accepted that the aerodynamic diameter of a particle is one of the main factors that detrmines particle deposition into the human respiratory system. The determination of aerodynamic diameter of spheres or near spherical objects is routinely accomplished using impactors. The aerodynamic diameter of man made organic fibers (MMOF), on the other hand, has not traditionally been measured using impactors, because fibers of the same cross section may have different lengths and a variety of shapes (straight, curved, etc.) for each length. The aerodynamic size of the fibers is thus a function of fiber orientation. Single and multiple stage impactors have been developed, calibrated, and validated specifically for the determination of the aerodynamic diameter of laerge fibers with circumscribed diameters between 20 and 35 #mu#m and an aspect ratio ragning from subfiber lengths (aspect ratio <3) up to 40. The impactor allows measurments of the aerodynamic diameter of cellulose acetate fibers released during mechanical smoking of cigarettes. The perfomance characteristics were evaluated by spherical particles of known diameters, fibers of known length and diameter, andcomputational fluid dynamic calcualtions. Our methodology has shown that interial ipactors can be used to determine the aerodynamic diameter of laerge cellulose acetate fibers.
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