Nowadays, clean rooms have been widely used in electronics, aerospace, machinery, chemical, pharmaceutical, food, medical, biological engineering. With the rapid development of the national economy and scientific research, the application of air shower rooms and clean rooms will become more widespread and more important.
Clean rooms can be classified according to the airflow pattern and use purpose and the main object of control: vertical unidirectional flow is the airflow pattern from the ceiling to the floor at a certain speed (0.25m / s ~ 0.5m / s). This airflow can create cleanliness levels of 100, 10, 1 or higher.
However, the initial investment is very high and the operating cost is very high. In the project, the area is minimized as much as possible and the necessary parts are used. Horizontal unidirectional flow is the airflow pattern at a certain speed (0.3m / s ~ 0.5m / s) from one wall to the opposite wall. This airflow creates a purification level of 100. Its initial investment and operating costs are lower than those of the vertical unidirectional flow pattern. The four major technical elements of a clean room are: coarse efficiency, medium efficiency and high-efficiency three-stage filtration, enough purification air supply, establishment and maintenance of indoor positive pressure, and the setting of terminal high-efficiency or ultra-high-efficiency filters.
To achieve the required cleanliness, filtering, intercepting, and adsorbing particles are essential. High-efficiency air filters are also necessary in clean room applications.
Clean room HEPA filter has a collection efficiency of 99.9% or more and a flow resistance of 250Pa or less for particles with a particle size of 0.3μm or more under the rated air volume. ULPA (ultra-low penetration air filter) is an air filter with a collection efficiency of 99.999% and a flow resistance of 280Pa or less at a rated air volume of 0.1 to 0.2μm.
For ISO5 unidirectional flow, an ISO40 H-class high-efficiency HEPA air filter should be used (minimum penetration particle size retention rate 99.99%). For non-unidirectional flow below ISO5, an ISO35 H-class high-efficiency filter (minimum penetration particle size retention rate 99.95%) should be used.
High-efficiency filters at the end of air-conditioning systems (including partitions with partition filters) should not use hydrophilic materials, and should not choose materials that are prone to breed microorganisms. The filter material of the high-efficiency filter is generally glass fiber, but it should not contain glass fiber with high sodium and potassium content which is easy to drop. A pre-filter should be installed in the air supply system, and the pre-filter retention efficiency is not less than 90%. The pre-filtration section should have a simple and practical resistance monitoring device, which can accurately and intuitively provide information on clean room filter replacement.