With the fast development of semiconductor, pharmaceutical, food, and other industries, attention has been shifted from the particulate pollution in the past to the chemical pollution recently. For the control object related to the air cleanliness, it has been shifted from single object, i.e., particles in the past, to two objects which also include airborne molecular contaminant (AMC). In fact standard related to air cleanliness and classification of air cleanliness has contained both the particle concentration level (customarily it is still called air cleanliness level) and the AMC concentration level. However, the air cleanliness specifically related to particle concentration level is still the core index to evaluate the air cleanliness of the environment.
Classification of Air Cleanliness