Filters are categorized as follows: Pre-filters (commonly referred to as Class G), Medium-efficiency filters (commonly referred to as Class F), and High-efficiency filters.
Pre-filters are further divided into: G1, G2, G3, and G4 (G4 has the highest filtration efficiency, followed by the others).
Medium-efficiency filters are divided into: F5, F6, F7, and F8 (F8 has the highest filtration efficiency, followed by the others).
High-efficiency filters are divided into: Class 300,000 filters, Class 100,000 filters, and Class 100 filters (Class 100 filters have the highest high-efficiency filtration efficiency, followed by the others).
The mainstream filters on the market include: non-woven fabric filters, belt filters, metal filters, paper filters, nylon mesh filters, glass fiber filters, and 3M filters (a low-resistance, high-efficiency, energy-saving filter introduced by 3M in recent years).
Airborne dust affects human health and product quality, especially in specialized industries such as precision instruments, electronics, pharmaceuticals, and hospitals, where extremely high air cleanliness requirements are necessary. This necessitates the selection of combined air handling units tailored to the specific requirements of different industries.
Air used in comfort-oriented air-conditioned environments has certain requirements regarding dust content. Generally, the indoor dust concentration is specified to be 0.15–0.25 mg/m³, and particles ≥10 μm should be filtered out. For these types of air handling units, only coarse and medium-efficiency filters are needed. However, for the aforementioned specialized industries, high-efficiency filters are required to achieve ultra-clean purification. These purification requirements are very high, and the indoor air dust concentration is expressed as particle count concentration (particles/L).
