Mass concentration measurements of airborne suspended particulates have been made on the filtering method. On the otherhand, a light scattering method has been adopted in Japan for the routine monitoring. However, this method has a few defects. In the cases where the system of particulates changes or mist exists in the air, the mesured concentrations are effected and for accurate measurements the calibration procedure is required relating the filtering method.
This paper describes on the characteristics of the dust monitor using a piezoelectric microbalance method, and shows its superiority over the light scattering method. The correcting method of mass sensitivity in this instrument, which is very important for practical use, has been developed applying water-soluble rhodamine. The collection efficiency of sample dusts (quartz powder, polystylene latex and lead fume) in this detector and the effects of relative humidity on measured concentrations are verified in this experiment.
It is proposed that the instrument should be equipped with the humidity regulator for practrical measurement corresponding to the governmental environmental standard of suspended particulates.

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Characteristics of impact fracture of particles was experimentally investigated by shot life tester of centrifugal blowing force type.
Cast steel shots and glass beads were used for test particles.
The relation between the weight and the diameter frequency distribution of fractured particles was obtained.
It was found that ductile cast steel shots had three stages of fracture process, while bridle glass beads had one stage of it.

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In order to control air pollution in automobile exhaust particulates, the authors applied the electrostatic precipitator (E. P.) to the gasoline engine. The trial E. P. have two features to be mounted on the automobiles. The first point is the compact design of E. P. The other point is high voltage power source was supplied from car's battery by a method of using the trial DC-AC invertor. In this study two kinds of engines have been used; one is 4 cycle engine, Nissan Prince 1500cc, and the other is 2 cycle engine, Suzuki Fronte 360cc. The test was perfomed under no load driving.
The results are summarized as follow:
1) Collection efficiency was rather satisfactory.
2) Particle size distribution of 4 cycle engine exhaust showed to obey log-normal distribution. and it's particle size was mostly to be so much smaller than 1μm diameter.
3) About 35 percent of lead supply in fuel were emitted under our condition. The remainder were accumulated in the engine and exhaust system as deposit.
E. P. is available in air pollution control. We have the dawn of hope for applying the E. P. to the gasoline engine.

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