The main function of a clean room is to control the cleanliness level and temperature-humidity of the atmosphere that the products (such as silicon chips, etc.) come into contact with, so that the products can be produced and manufactured in a good environmental space. This space is called a clean room. According to international practice, the clean level of a clean room is mainly determined based on the number of particles with diameters greater than a certain standard in each cubic meter of air. That is to say, a clean room is not 100% dust-free, but is controlled at a very low level. Of course, the standard of this dust content is already very small compared to the common dust, but for optical structures, even a little dust can have a very significant negative impact. Therefore, in the production of optical structures, cleanliness is an inevitable requirement.
1. Outdoor air dust concentration In air purification technology, the most common method is to use the number of dust particles with a diameter of 0.5 μm or larger as the counting concentration. For outdoor atmospheric dust concentration, there are significant regional differences, and it can be statistically categorized into three typical regions. Through a large amount of statistical data analysis, the counting concentrations of outdoor dust in these three typical regions of our country are: Industrial cities: The counting dust concentration is generally not more than 3X105 particles/L, and the maximum is approximately 106 particles/L (belonging to a severely polluted level); Rural areas outside the city (excluding industrial areas outside the suburbs): The counting dust concentration is generally not more than 2X105 particles/L; Non-industrial areas or rural areas: The counting dust concentration is generally not more than 1X105 particles/L. A large number of studies have shown that for clean rooms with an efficient air purification system at 100 levels and below, when the atmospheric dust concentration changes within 106 particles/L, the impact on the dust concentration in the clean room can be ignored, so when conducting purification design calculations, 106 particles/L is usually taken as the outdoor atmospheric dust concentration, which is also a safe choice in engineering treatment.
2. Indoor unit volume dust emission rate The dust emission rate in the operating room mainly includes the dust emission from people and building surfaces, equipment surfaces, etc. Practice has shown that the dust emission from people is the most significant, and the influence of people's activities on the dust emission is also significant. Generally, in design calculations, it can be taken as follows: When people are stationary: The dust emission is 105 particles/(P·min) When people are active: The average dust emission is 5x105 particles/(P·min) Ground surface dust emission: 1.25x104 particles/(9min·m2) When people are stationary: 2 Layout of the clean operating room At present, the purification grades of domestic clean operating rooms are generally four levels: 100, 1000, 10000, and 100000. A few exceed 100 levels and a few are below 100000 levels. Clean operating rooms can be arranged as single-directional flow clean rooms, quasi-single-directional flow clean rooms, and turbulent flow clean rooms according to the requirements of indoor cleanliness.
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