The air sampler for measuring the mass concentration of suspended particulate matter in the atomospheric air has been required to separate the coarser particles over 10 microns by the standard of environmental control.
This paper describes about the performance of particle classifiers (for 10 microns cut) attached on the air sampler for this purpose.
The classifiers prepared for the experiments are those of centrifugal, gravitational and cyclone types.
Studies are made for the comparison of the separation characteristics of these classifiers and on the view of 10 microns cut, with some experiments and numerical calculations.
The results are as follows;
(1) As well known, the accuracy of separation of the classifiers is more conveniently compared with a fractional separation efficiency.
(2) On authors' experiments about sampling in the atmospheric air, the ratios C_i/C_o shows some dispersion.
(Here C_o: Concentration containing the coarser particles C_i: Cut concentration)
(3) The air sampler with classifier, which is designed at 10 microns of 50% critical particle size, shows reasonable value of the mass penetration.
(4) It is thought that the centrifugal type classifier is practically reasonable as the particle classifier of the air sampler.

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To demonstrate the applicability of light-scattering for the examination of aerosol particles, the present paper described the outlines of a few of our recent studies. The following three problems are dealt with on the basis of theoretical computation of light scattering intensities and some additional experiments: (a) determination of size distribution by measuring the intensity of scattered light at three angles for a fixed wavelength of the incident beam; (b) determination of number concentration by measuring the absolute angular scattering intensities with a standard opal glass diffusor; and (c) direct estimation of approximate weight concentration from the measurements of angular scattering intensities.

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In order to measure the concentration and the size distribution of mist entrained in a chemical apparatus, a instrument with a new idea has been developed.
The sampling gas containing mist is fed into the cell and the purge gas is spouted from the core in the direction rightly opposite the inlet of sampling gas.
The cut size was varied in the range between 10 and several hundreds micron by changing the velocity of the purge gas from 0 to 15m/sec. The experiment suggests that the instrument with the described principle is a quite promising particle analyzer not only for mist but also for any kind of particulate material.

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