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.