Since the outbreak of the new crown pneumonia epidemic, fresh air products have become one of the most concerned products of the whole people. People are always thinking about whether they need to install a fresh air system to remove viruses and bacteria in the indoor air. In addition to ventilation, the most important function of the fresh air system is to filter pollutants in the air. Therefore, the filter of the fresh air system is the most important part of the entire system. The quality of the filter directly affects the quality of indoor air.
According to the grade, principle and material, the filter type of the fresh air system can be divided as follows:
1. According to the filtering grade
The general fresh air system filter can be divided into three levels, namely the primary filter, the medium efficiency filter and the high efficiency filter.
Primary filter: filter outdoor large particles of dust and insects.
Medium-efficiency filter: filter small particles such as outdoor pollen.
High-efficiency filter: HEPA, a filter that meets HEPA standards.
Can filter most dust above 0.3 microns. Many fresh air systems claim to have a filtration efficiency of over 99%, which is actually the test result after several times of filtration. When investigating the filtering effect of the product, you must keep your eyes open.
In the fresh air system, the primary, medium, and high-efficiency filters are generally not used alone, but two or three are used together. A fresh air system with more than two layers of filters can achieve better air filtration effects.
2. According to the filtering principle
At present, the common filtering principles are divided into two types, one is the physical filtering method, and the other is the electrostatic filtering method.
Physical filtration: common filter materials have different levels from G1 to H13. The higher the level, the greater the wind resistance, the more thorough the filtration, and the more expensive.
Electrostatic dust collection: PM2.5 has good filtering effect and low wind resistance, so there is no need to replace the filter frequently. The disadvantage is that it is inevitable to produce ozone, and when ozone reaches a certain level, it is harmful to the body. Therefore, electrostatic dust collection must have strict requirements on the amount of ozone produced, and must choose products that meet national standards and pass quality.
Among the fresh air systems, the physical filtration method is currently the most used, and the filter needs to be replaced regularly, otherwise a good filtration effect cannot be achieved. The electrostatic dust collection method is in the popularization stage. Some large manufacturers have developed or are developing related functions. It is expected that this filtering method will be widely used in recent years.
3.According to the filter material classification
Non-woven fabric filter: scientific name polyester fiber, commonly known as non-woven fabric, non-woven fabric has technical characteristics such as wide use, technical maturity, and good stability. It is my country's current primary and medium-efficiency plate and bag filter The typical filter material. The manufacturing process is made by melt-blown, needle punch, spunlace, spunbond and other processes through multiple processes. Compared with other filters of the same level, it has stable quality, larger dust holding capacity, strong moisture resistance, long service life, and economical Durable and other advantages. Non-woven fabrics are also the earliest filter materials used. In recent years, due to the continuous advancement of technology, the emergence of composite non-woven fabrics has greatly improved the low-cost and low-end image of non-woven fabrics, and can reach sub-high efficiency in terms of efficiency.
Glass fiber filter screen: The glass fiber filter screen is mainly made of glass fibers of various thicknesses and lengths through special processing technology. Glass fiber is characterized by its stable performance, high temperature resistance, high efficiency, large capacity, and long service life. And in some special circumstances, only wave line can do the job. It is widely used in the primary effect filter, high temperature resistant filter and high efficiency filter of general ventilation system.
Synthetic fiber filter: It can fully replace non-woven fabric and glass fiber under normal filtering environment, covering a full range of coarse, medium and high-efficiency filter products. It is an emerging filter material and the main development direction of future filter materials. Compared with other filters of the same level, it has the advantages of small resistance, light weight, large capacity, environmental protection (can be incinerated), and moderate price.
Activated carbon filter: It has the high-efficiency adsorption performance of activated carbon and can be used for air purification to remove volatile organic compounds formaldehyde, toluene, hydrogen sulfide, chlorobenzene and pollutants in the air. The activated carbon filter screen adopts aluminum honeycomb, plastic honeycomb and paper honeycomb with through-hole structure as the carrier. 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 polyurethane foam loaded with powdered activated carbon, and its carbon content is about 35%-50%. The air resistance is small, the energy consumption is low, it can deodorize, deodorize, and purify the environment under a certain air volume, and has a good purification effect. In use. Generally, it must be used with independent primary and medium-efficiency filters.
Nano-silver filter screen: the silver ion antibacterial agent with a diameter of 100nm is added to the master batch, and then drawn and woven into a filter screen, so that each mesh of the filter has antibacterial properties. High antibacterial performance, up to 99%. The filter is easy to clean, and the antibacterial performance does not decrease after washing.
Photocatalyst filter: using nano-titanium dioxide photocatalyst as raw material, combined with the latest technology to make the photocatalyst evenly adhere to the surface of different materials with the smallest particles. Photocatalyst uses sunlight, fluorescent lamps, and ultraviolet light as energy sources to stimulate electrons in the valence band (e-) Transition to the conduction band, generate corresponding holes (h+) in the valence band, generate active oxygen and hydroxyl radicals with strong oxidation, and pollute harmful organic substances such as formaldehyde, methylamine, benzene, xylene, TVOC, etc. Oxidation and decomposition of substances, odors, bacteria, etc. into harmless CO2 and H2O to achieve the purpose of purifying the air and decomposing harmful organic matter.
Generally speaking, non-woven fabric filters and glass fiber filters are mostly used as primary filters, while synthetic fiber filters, activated carbon filters, nano silver filters, and photocatalyst filters are mostly used as medium-efficiency and high-efficiency filters. A better quality fresh air system will be equipped with more than two layers of filters to efficiently filter air pollutants.