In the clean zone, the pressure difference between each room relative to the outdoor atmosphere is called "absolute pressure difference". The pressure difference between each adjacent room and adjacent area is called "relative pressure difference", or "pressure difference" for short. The role of "pressure difference": Because air always flows from a place with a high absolute pressure difference to a place with a low absolute pressure difference, we must ensure that the higher the absolute pressure difference in the room with the higher the cleanliness, the lower the absolute pressure difference in the room with the lower the cleanliness. In this way, When the clean room is in normal work or the airtightness of the room is damaged (such as opening the door), the air can flow from the area with high cleanliness to the area with low cleanliness, so that the cleanliness of the room with high cleanliness level is not affected by the cleanliness of low-level rooms. Air pollution and interference. Because this kind of pollution and cross-contamination are invisible and ignored by many people, at the same time, this kind of pollution is very serious and irreversible. Once it is contaminated, there are endless troubles. Therefore, we list the air pollution in clean rooms as the “second largest source of pollution” after “human pollution.” Some people say that this type of pollution can be solved by self-purification, but self-purification takes time. In an instant, if it pollutes the room’s equipment The facilities and even the materials have been contaminated, so self-purification has no effect. Therefore, the necessity of ensuring the pressure difference control is obvious. The fresh air system is an independent air treatment system composed of a fresh air ventilator and pipeline accessories. The fresh air ventilator filters and purifies the fresh outdoor air and transports it to the room through the pipeline. At the same time, it removes the dirty and low-oxygen air in the room to outside.