Select Your Class of Cleanroom & Expression of the cleanliness level

Cleanliness of the cleanroom is generally expressed in the number of particles

contained in the unit volume of air. Therefore, the smaller the numbers of the cleanliness class, the higher the grade (less dust) 

of the cleanroom. For the standard of cleanliness, the U. S. Federal Standards (FS-209D E) were used generally 

but has been abolished when ISO14644 has been enacted (2000). However, the cleanliness class based on FS 209D is still widely 

used in actual cleanrooms. This expresses the fine-particulate concentration as the number of particles 

in 1 cubic foot (pieces/ft3). Although the standard particle size is 0.5 μm in the FS-209D standard.