The guideline contains the classification of air cleanliness for cleanrooms and associated controlled environments in mathematical, tabular and graphical form. The guideline covers exclusively the maximum concentration of airborne particles at the clean work place. Following the classification according to DIN EN ISO 14644, only particles within the specified size range 0,1 ?m and 5 ?m are considered. This guideline cannot be used to characterize the physical, chemical, radiological, or viable nature of airborne particles.