According to the filtration grade, the fresh air fan filter can be divided into three levels, i.e. primary filter, medium filter and high efficiency filter.

1. Primary filter screen: filter the large particles of outdoor dust and insects.
2. Medium efficiency filter screen: it can filter small particles such as outdoor pollen.
3. High efficiency filter: HEPA, HEPA standard filter.

In the fresh air system, the primary efficiency, medium efficiency and high efficiency filters are generally not used alone, but two or three are used together. The fresh air system with more than two filters can achieve better air filtration effect.

According to the filtration principle, there are two commonly used filtration principles, one is physical filtration, the other is electrostatic filtration.

1. Physical filtration: filtration materials are usually graded from G1 to H13. The higher the grade, the greater the wind resistance, the more thorough the filtration, and the more expensive the price.

2. Electrostatic precipitator: PM2.5 has good filtering effect, small air resistance, and does not need to change the filter screen frequently. The disadvantage is that it will inevitably produce ozone, which is harmful to health. Therefore, the strict requirements of electrostatic precipitator ozone generation, must choose in line with national standards, products.

1. Non-woven fabric, polyester mesh. The non-woven fabric has the technical characteristics of wide technology, mature technology and good stability. It is a typical filter material of medium efficiency and bag filter in China. The manufacturing process is melt blown, needle punched, Spunlaced and spunbonded. Compared with other filter materials of the same grade, it has the advantages of stable quality, large dust capacity, strong moisture resistance, long service life, economy and durability. Non woven fabric is also the earliest used filter material. In recent years, due to the continuous development of technology, the appearance of composite non-woven fabrics has greatly improved the image of low-cost and low-grade non-woven fabrics, and has achieved sub high efficiency in efficiency.

2. Glass fiber filter: glass fiber filter is mainly made of various glass fibers with different thickness and length by special processing technology. Glass fiber has the characteristics of stable performance, high temperature resistance, high efficiency, large capacity and long service life. And in some special cases, only wave line can be competent. Widely used in general ventilation system, primary filter, high temperature resistant filter and high efficiency filter.

3. Synthetic fiber filter screen: it can completely replace the non-woven fabric and glass fiber in the general filtering environment, covering a full range of coarse, clean and efficient filtering products. It is a new type of filtering material and the main development direction of filtering materials in the future. Compared with other filter materials of the same grade, it has the advantages of small resistance, light weight, large capacity, environmental protection (incineration), moderate price, etc.

4. Activated carbon filter screen: with high adsorption performance of activated carbon, it can be used for air purification, removing volatile organic compounds formaldehyde, toluene, hydrogen sulfide, chlorobenzene and air pollutants. The activated carbon filter screen adopts aluminum honeycomb, plastic honeycomb and paper honeycomb as carriers. Compared with the traditional activated carbon filter, it has better aerodynamic performance, small volume density, large surface area, high adsorption efficiency and small wind resistance coefficient. The honeycomb activated carbon filter is made of powdered activated carbon on polyurethane foam, and its carbon content is about 35%-50%. Small air resistance, low energy consumption, in a certain amount of air can deodorize, clean the environment, purification effect is good. In use. Generally, it must be used with independent primary and medium efficiency filters.

5. Nano silver filter screen: add 100 nm silver ion antibacterial agent into the masterbatch, and then weave the filter screen by wire drawing, so that each screen wire of the filter has antibacterial performance. High antibacterial activity, up to 99%. The filter is easy to clean, and the antibacterial performance does not decline after cleaning.

6. Photocatalyst filter screen: nano titanium dioxide photocatalyst is used as raw material, combined with * *, and the photocatalyst is uniformly attached to the surface of different substances with the smallest particles. The photocatalyst uses sunlight, fluorescent lamp, and ultraviolet light as energy sources to excite the electron (E -) in the valence band to transition to the conduction band, and generate the corresponding hole (H) in the valence band to produce reactive oxygen species and strongly oxidized hydroxyl radicals. Formaldehyde, methylamine, benzene, xylene, TVOC and other harmful organic compounds, pollutants, odors and bacteria are oxidized into harmless CO2 and H2O to purify air and decompose harmful organic compounds.

Generally speaking, non-woven fabric filter and glass fiber filter are mostly used as primary filter, while synthetic fiber filter, activated carbon filter, nano silver filter and photocatalyst filter are mostly used as medium efficiency filter and high efficiency filter. The fresh air system with better quality will be equipped with more than two layers of filters to effectively filter air pollutants.