Air filter is the most important unit in clean room AHU system configuration. A proper installation of different filters will greatly improve the air cleanness whichis crucial for activities in this area.
Air filters are available in multiple grades according to filtration efficiency, mainly including primary filters, medium efficiency filters, high and medium efficiency filters, sub-high efficiency filters and hepa filters. Filters of different levels differ in filtration efficiency and applicable occasions.
Primary filter: Mainly used to filter large dust particles ≥5.0μm and various solid particles as the primary filter of the air purification system to protect the medium filter. It has a simple structure and is cheap. It is often placed at the fresh air inlet of the air conditioning equipment or after the fresh air and return air are mixed.
Medium efficiency filter: Mainly used to filter medium-sized dust particles ≥1.0μm as a pre-filter for hepa filters to protect hepa filters and improve air cleanliness. Medium efficiency filters have large air volume, low resistance, and a solid structure, and are often used in air conditioning systems with higher requirements.
Sub-high efficiency filter: used to filter 0.5~0.1μm microparticle dust, can effectively filter out bacteria, suitable for ultra-clean and aseptic purification occasions. The air passing through the hepa filter must be pre-filtered by the primary and medium efficiency filters.
Hepa filter: used to filter fine dust particles smaller than 0.1μm, with high efficiency and low resistance, suitable for the final stage of air supply in ordinary clean rooms above Class 100. High-efficiency filters have a simple structure and light weight, and are often located before the end air outlet of the system.
Applications and characteristics of different grades filters
- Primary filter: Applicable to occasions where large dust particles need to be filtered, such as laboratories, hospitals and other environments that require high cleanliness. Its filtration efficiency levels are G1, G2, G3, and G4. The higher the level, the higher the filtration efficiency3.
- Medium efficiency filter: Applicable to air-conditioning systems that need to filter medium particles, such as office buildings, shopping malls, etc. The filtration efficiency levels of medium efficiency filters are F5, F6, F7, F8, etc.1.
- Sub-high efficiency filter: Applicable to ultra-clean and sterile purification occasions, such as semiconductor production workshops, biosafety laboratories, etc. The filtration efficiency level of sub-high efficiency filters is usually higher than H114.
- Hepa filter: Applicable to ordinary clean rooms and sterile operating environments, such as pharmaceutical workshops, food processing plants, etc. The filtration efficiency level of high efficiency filters is usually H13 or higher14.
Here’s the comparison table of the filtration standards from different nations. By understanding the characteristics and applicable occasions of filters of different levels, we can better choose the appropriate air filter to ensure the best air purification effect.
