Respirable fraction, i.e., particle penetration through the tracheobronchial region, P(TB)
, in adults and a 10 yr-old child. Data are daily averaged values for a median activity level, gradual augmenter breathing habit, and uncorrected for particle inhalability. Child-A and child-B are for a scaling factor of 1.0 and 1.26 in Equations 2 and 3, respectively. Horizontal red line highlights 50% penetration which occurs at 2.7 μm (adult female), 3.1 μm (adult male), 3.6 μm (child-B), and 4.4 μm (child-A).