Inhalability of large solid particles

摘要

Large particles (10-150 #mu#m) with systemic toxicity pose a health risk if inhaled regardless of where they deposit. This research seeds to better define particle inhalability, the fraction of airborne particles that are ihaled as a function of particle size. Measurements of inhalability were made for solid particles using a 1.6 X 1.6 X 5-m wind tunnel. Tunnel air velocities were 0.4, 1.0, and 1.6 m/s. A full-size, full-torso mannequin was used to collect dust entering either the mouth or nose for breating at minute volumes of 14.2, 20.8 , and 37.3 l. The mannquin either faced the oncoming wind or rotated slowly (0.06 rpm) rpm) during sample collection. At the test section, air velocity was uniform to within 10% and aerosol concentration was uniform to within 15% over the central 80% of the cross section. Orientation-averaged inhalability for mouth breathing was higher than the inhalable particlate mass (IPM) sampling criterion for particles smaller than 35 #mu#m and lower than the criterion for larger particles, leveling off at about 30% for particles > 70 #mu#m. Facing-the-wind mouth inhalability showed the same trend as the IPM sampling criterion, but the measured values were 25% higher. Wind velocity and breathing pattern had little effect on inhalability for the range of conditions examined here. Orientation-averaged inhalability for nose breathing dropped quickly with particle size reaching less than 10% at 60% #mu#m. Facing-the-wind nose inhalability was slightly increased for particles smaller than 60 #mu#m compared to orientation averaged inhalability for nose breathing.