There are three grades of air cleanliness, namely 100, 1000 and 10000. The lower the grade, the neater it will be. For example, the air cleanliness of some operating rooms such as organ transplantation and heart surgery is 100, that of some operating places such as ophthalmology and plastic surgery is 1000, and that of thoracic surgery, urology and obstetrics and gynecology is generally 10000.

There are three methods to detect air cleanliness, namely, empty state, static state and dynamic state, and the distinction can be judged by the maximum concentration limit of particulate matter considered in unit volume of air.

The air cleanliness is judged according to the dust content and concentration in the air environment, and the air cleanliness is also determined according to the dust content in the air.