Fig. 2.

The breathing pattern. The breathing protocol, illustrated by breathing data for a standard measurement, recorded at 100 Hz. The protocol starts with a period of tidal breathing of particle free air. The breathing manoeuvre is initiated with exhalation to RV followed by an inhalation of the test aerosol to TLC, a breath-hold of 10 s and then relaxed exhalation. A sample is collected from the exhaled air after a controlled volume has passed the sample collector. The particle number concentration is monitored continuously in the test aerosol until the inhalation, and then determined in the exhaled sample immediately after exhalation. The aerosol residence time in the lungs is calculated from the recorded breathing pattern