ABSTRACT
Standard powders for industrial use generally have fairly narrow size distributions. There are several standard particles currently in scientific use. For example, uniformly sized spherical polystyrene latex particles are used as a calibration standard in electron microscope studies. Japan has also defined many types of standard powders and particles for industrial tests as the Japanese Standard Powders Z 8901. They are sold by the Association of Powder Process Industry and Engineering, Japan. The particle size distribution includes the uncertainty region based on statistical theory. The committee of Association of Powder Process Industry and Engineering, Japan, recognizes the particles as a standard reference particle in Japan. Natural pollens and spores are also mono-sized and nearly spherical, but they are sometimes swelled by moisture and have irregular surfaces. In the United States, AC fine and coarse dusts are defined by the Society of Automotive Engineers and are utilized for performance tests of automobile air cleaners.
