This Standard specifies the classification of air cleanliness in cleanrooms and associated controlled environments exclusively in terms of concentration of airborne particles, and its evaluation method. Only particle populations having cumulative distributions based on threshold (lower limit) sizes ranging from 0.1 mum to 5 mum are considered for classification purposes. However, concentrations of ultrafine particles (particles smaller than 0.1 mum) and macroparticles (particles larger than 5 mum) may be used to quantify these populations in terms of U descriptors and M descriptors, respectively. This classification shall not be used in order to characterize a physical and chemical nature of airborne particles. Furthermore, the relation between the particle size and maximum permitted concentration specified in this Standard are intended for classifying, and do not express the actual particle size distribution.

JIS B 9920:1989

JIS B 9920:1989

ISO 14644-1:1999 - Identical