What is a clean air system?
A clean air system is a general term for a system that manages the air
cleanliness so that the amount of dust, dirt and airborne microorganisms
(contaminants) in the air in a limited space falls below a certain standard.
Depending on the size and application, it is classified into equipment
and facilities such as "clean benches."
Generally, a clean bench needs to have an airtight structure that surrounds a clean air zone so that contaminants do not enter it.
Air Cleanliness Class
The degree of air cleanliness of a space created by a clean air system is expressed by the "air cleanliness class." Currently, in Japan, the US Federal Standard (FED. STD. 209) and the ISO standards (ISO 14644-1) are used together as the air cleanliness class standard. The widely used US Federal Standard was abolished in 2001, and now the international standard, ISO, is becoming mainstream.
According to the US Federal Standard, the number of fine particles having a diameter of 0.5μm or more contained in one cubic foot is specified and classified from Class 1 to Class 100,000. On the other hand, in the ISO standard, the air cleanliness class is graded according to the number of fine particles having a particle size of 0.1μm or more in one cubic meter, and classified into classes 1 to 9.
◆ISO Standards（ISO14644-1）
Selection of clean air systems based on "actual cleanliness"
"Actual cleanliness" refers to the air cleanliness when workers are actually working with the use of a clean air system. On the contrary, the air cleanliness when there is no worker or equipment inside the clean air system, which is not in use, is called "nominal cleanliness."
When you are preoccupied with only the nominal air cleanliness to control the clean air environment, a high level of actual air cleanliness may not be maintained during the operation because the contaminants generated inside may not be discharged into the outside. A clean air system that can produce a high nominal air cleanliness is of course important, but the contaminants that you would normally want to prevent in a clean air environment are generated during the actual work.
When installing a clean air system, it is important to think primarily of maintaining a high level of actual air cleanliness as well as nominal air cleanliness by selecting, for example, one with a structure that allows dust and dirt (contaminants) generated by work to be quickly discharged.