Abstract: A method and apparatus for determining the deposition of particles in the respiratory tract and/or for checking the operating function of the respiratory tract by means of pulses of gases or aerosols injected into a stream of air inhaled by a test patient and by obtaining a measuring signal in each of the inhaled and exhaled streams. The main stream of the inhaled and exhaled air is conducted directly through a band of light (3), and the region of the intersection of the band of light with at least part of the inhaled and exhaled streams is placed in the object plane of an optical image system for a light measuring device. Either the individual pulses generated by the individual particles in the inhaled and exhaled streams or the scattered radiation emanating from the gases and aerosols in these streams is measured to obtain the ratio of the exhaled to the inhaled numbers of particles and/or the concentration profile in the inhaled and exhaled streams.

Abstract: An ultramicroscopic spectrometer for examining properties of aerosol particles includes a receptacle having a wall defining a measuring chamber; an aerosol jet generating arrangement for forming an aerosol jet from the particles by aerodynamic focusing; a mount supporting the aerosol generating arrangement in the measuring chamber; a first passage in the receptacle wall for passing an incident illuminating beam through the receptacle wall into the measuring chamber; and a second passage in the receptacle wall for passing an information beam respectively an observation beam of the aerosol jet through the receptacle wall from the measuring chamber. The axes of the illuminating beam, the information beam and the aerosol jet intersect in a measuring field.