Clean Room, also known as a clean room or purification room. It is the foundation of pollution control, and without a clean room, it is impossible to mass produce pollution sensitive parts. In FED-STD-2, a clean room is defined as a room with air filtration, distribution, optimization, construction materials, and devices, where specific operating procedures are established to control the concentration of suspended particles in the air, thereby achieving appropriate levels of particle cleanliness.

1. Air supply cleanliness

To ensure that the cleanliness of the air supply meets the requirements, the key is the performance and installation of the final filter in the purification system.
The final filter of the purification system generally adopts high-efficiency or sub high-efficiency filters. According to the Chinese standard, the efficiency of high-efficiency filters is divided into four levels: Class A is ≥ 99.9%, Class B is ≥ 99.9%, Class C is ≥ 99.999%, and Class D is (for ≥ 0.1) μm particles) ≥ 99.999% (also known as ultra high efficiency filters); The sub high-efficiency filter is (for ≥ 0.5) μm particles) 95-99.9%. The higher the efficiency, the more expensive the price of the filter. So when choosing a filter, it should be based on both meeting the cleanliness requirements of the air supply and considering economic rationality. From the perspective of cleanliness requirements, the principle is to choose low-performance filters for low-level cleanrooms and high-performance filters for high-level cleanrooms.

Generally speaking, a high and medium efficiency filter can be selected for a 1 million level filter; Below 10000 levels, sub high efficiency or Class A high efficiency filters can be selected; Class B filters are selected for grades 10000 to 100; Class C filters are selected for grades 100 to 1. There seem to be two types of filters to choose from for each cleanliness level here. The choice of high-performance or low-performance filters depends on the specific situation: when environmental pollution is severe, the indoor exhaust proportion is large, or the clean room is particularly important and requires a large safety factor, in either or both of these cases, a higher type of filter should be selected; On the contrary, lower performance filters can be selected. For 0.1 μ For clean rooms that require control of particles, regardless of the concentration of particles being controlled, a D-type filter should be selected. The above is only from the perspective of filters. In fact, to choose a good filter, it is necessary to comprehensively consider the characteristics of the clean room, filter, and purification system.

To ensure the cleanliness of the air supply, only qualified filters are not enough, and it is also necessary to ensure:
a. Do not damage the filter during transportation and installation;
b. Tight installation. To achieve the goal of 'a', construction and installation personnel are required to be well trained, with knowledge of installing purification systems and proficient installation skills. Otherwise, it will be difficult to ensure that the filter is not damaged, and there are profound lessons to be learned in this regard.

Secondly, the issue of installation tightness mainly depends on the quality of the installation structure type. The design manual generally recommends that for a single filter, an open installation type should be used, so that even if leakage occurs, it will not leak into the room; The use of finished high-efficiency air supply vents ensures easy tightness. In recent years, liquid tank sealing and negative pressure sealing have been commonly used for air filters with multiple filters.
The sealing of the liquid tank must ensure that the joint of the liquid tank is tight and the overall framework is on the same level. Negative pressure sealing is to keep the outer periphery of the joint between the filter and the static pressure box and the frame in a negative pressure state, similar to the surface mounted type, even if it leaks, it will not leak into the room. In fact, as long as the installation frame is flat and the contact between the filter end face and the installation frame is even, it should be said that it is not difficult for any installation type to achieve the installation tightness requirements of the filter.