A clean room is a space in which the concentration of airborne particles is kept at a very low, defined level. As a rule, either the protection of a product is the focus or personal protection.
If, for example, a product is to be protected, overpressure is used so that no particles from outside can reach the product. On the other hand, if the protection of persons is the main focus, then negative pressure is used so that no pathogens can leave the room.
In order to be able to classify the purity of a clean room, appropriate particle measurements are carried out. Cleanliness classes are defined, for example, in the standard ISO 14644-1. But also the GMP guideline, which plays a central role especially in the pharmaceutical industry, defines clean room classes.