Experimental studies of the deposition of particles in the human lungs.

: Measurements of deposition, De, during steady breathing through the mouth of particles between 0.5 and 2.5 micons diameter and density 0.92 g/cm3 show that it is related to the tidal volume, VT, expiratory reserve volume, Vr, and a "normal" volume, Vro, by the formula 100 De= Vt/B+C/FD- E- Vr-Vro/A where B, C, D and E are constants which depend on particle size but do not vary from subject to subject enough to have much influence on corresponding values of De. A and and Vro are independent of particle size but relate to the individual subject, especially Vro. A new method is described of correlating the numerous experimental results, which involve six variables, and of evaluating the subject's 'normal' expiratory reserve volume, Vro, for any subject.