Sufficient ventilation is to dilute and eliminate indoor polluted air. According to different cleanliness requirements, when the clean room height is high, the number of air changes is appropriately increased. Among them, the ventilation capacity of the 1 million-class clean room is considered according to the high-efficiency purification system, and the rest are considered according to the high-efficiency purification system; when the 100,000-class clean room high-efficiency filter is concentrated in the machine room or the system end adopts the sub-high efficiency filter At the time, the number of air changes can be appropriately increased by 10-20%.
For the above recommended ventilation values, the author believes that the unidirectional flow clean room
has a low wind speed through the room cross section, and the turbulent flow clean room is a recommended value with a sufficient safety factor. The vertical unidirectional flow is ≥0.25m/s, the horizontal unidirectional flow is ≥0.35m/s, and the cleanliness is detected in the open state or static state. Although it can meet the requirements, the anti-pollution ability is poor. Once the indoors enter the working state, the cleanliness It may not meet the requirements. Such examples are not individual. At the same time, there are no fans in China's ventilator series that are more suitable for purification systems. Generally, designers often do not accurately calculate the air resistance of the system, or do not notice. Whether the selected fan is in a favorable working point on the characteristic curve, so that the air volume or wind speed will not reach the design value shortly after the system is put into operation. The US Federal Standard (FS209A~B) has been stipulated before October 27, 1987 that the airflow rate of the unidirectional flow clean room through the clean room section is usually maintained at 9Oft/min (0.45m/s) without interference throughout the room. Under the condition that the speed unevenness is within 20%, any significant decrease in airflow speed will increase the possibility of pollution between the self-cleaning time and the working position (all except the dust concentration after the FS209C was issued in October 1987). The parameter indicators are not specified). To this end, the author believes that it is appropriate to appropriately improve the current design value of the unidirectional flow velocity in China. Our unit has done this in the actual project, and the effect is still relatively good. The turbulent flow clean room is the recommended value with a sufficient safety factor, but many designers are still not assured. When doing the specific design, increase the ventilation capacity of the 100,000-class clean room to 20~25 times/h, 10,000-plus Up to 30~40 times/h, 1000 steps up to 60~70 times/h, this not only increases the equipment capacity, increases the initial investment, but also increases the maintenance and management costs in the future. In fact, there is no need to do this. do. In the preparation of China's air clean technical measures , more than 100 clean rooms in China have been investigated and tested, and many clean rooms are still tested under dynamic conditions. The results show that: 100,000 levels ≥ 10 times / h, 10,000 ≥ 20 times / h, 1000 level ≥ 50 times / h ventilation can meet the requirements. The US Federal Standard (FS2O9A~B) stipulates that non-unidirectional flow clean room (100,000 class, 10,000 class), room height 8~l2ft (2.44~3.66m), usually consider the whole room to be ventilated at least every 3 minutes ( That is 20 times / h). Therefore, the design specification  has considered a large wealth factor, and the designer can safely use the recommended value of the ventilation amount.