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| Clean rooms are classified according to the classes decided based on indoor air cleanness, and are arranged in a way that is appropriate for individual purposes. The classes are decided based on the quantity of suspended dusts in the indoor air. In America, the classification is based on the number of particles of dusts with the size of 0.5μm or larger in the air of 1ft³ according to the America's federal standards 209B as shown in Table 1. For example, when the number is 100, it means a cleanness level in which there are 100 or less suspended particles of dusts with the size of 0.5μm or larger in the air. In addition, when it comes to the concentration of microorganism, there is NHB 5340.2, a NASA's standard. |
