What is the clean room, cleanliness, and local space purification?

Clean room is defined as: the dust and microbial contamination regulations require environmental control of the room and area.
Local space purification refers to: only the indoor work area-specific local space of the space with suspended particulate concentration to achieve the required level of air cleanliness.
Cleanliness is defined as the number of permissible particles in the air per unit volume of a clean environment that is greater than or equal to one of the suspended particles.