As micro-particles floating in the air attach to products being manufactured, cause defects, act as a hindrance factor in the production of products to meet the purpose of use, and wield a huge influence on credibility and production costs in semiconductor manufacture, electronic industry, film factories, etc., such spaces should be maintained in clean state. In addition, environmental factors such as temperature, humidity, pressure, air flow, noise, and vibrations are important subjects to be controlled, and efforts should be concentrated on the improvement of quality and credibility and enhancement of yield of products compared with raw materials by controlling such factors