In this rapidly developing world, clean and sanitary air becomes an luxurious pursuit for modern people. The right air purifier can effective realize such pursuit. But how to choose a high-efficient air purifier?
Why is air purifier able to remove PM2.5?
Users who have heard about the air purifier would know that the structure of most air purifiers is quite simple. Main parts are motors, fans, and filters. When working, the fan blade is driven by the motor to circulate the indoor air. When the air with pollutants passes through the filter screen inside the purifier, the pollutants will be absorbed on the filter screen and fail to pass through. And the repeated operation in a period of time can purify the indoor air. This is the principle of passive adsorption filter air purifier, and also the method adopted by most air purifiers in the market.
Filter screen dominates the purifying efficiency of the air purifier.
User’s demand for air purifier is to remove PM2.5, therefore the air purifiers will carry HEPA Filter( High Efficiency Particulate air Filter) to filter particles. Since it is relative easy for particles with diameter above 0.5μm and below 0.1μm and quite hard to remove particles with diameter between 0.1μm~0.3μm, the industry defines the HEPA filter level based on the filtration rate of 0.3μm particles. According to the different filtration efficiency, most civil air purifiers use HEPA filters of H11(>98%) ~ H14(>99.997%). It does not mean that the higher the filtration efficiency of HEPA filter is, the better; because the more efficient the filter, the greater the wind resistance, and the less ventilation (more powerful fan motors are needed). As the air volume decreases, the time of purification per unit will also decrease, and the purification efficiency will therefore be reduced.
Therefore, CARD value (Clean Air Delivery Rate) is introduced as an international standard of air purifiers to represent the volume of air that can be purifier per unit time. The higher the CARD value is, the higher the purification efficiency is.
Active purification is better. Photo-catalyst becomes a hot topic.
Different from passive adsorption, active purifier can eliminate harmful substances such as virus, formaldehyde and bacteria by decomposition. Photo-catalyst technology is one of the most popular active purification technologies. Photo-catalyst is a general name of photo semiconductor material with photo-catalytic function which is similar to catalyst. It does not participate in reaction itself, and therefore no need to worry about the problem of consumables. In the market, most photocatalyst coats nanoscale titanium dioxide on the surface. Under the action of ultraviolet and visible light, nanoscale titanium dioxide can produce strong catalytic degradation function, effectively degrade toxic or harmful gases in the air, and kill various germs (strong oxidation damage cell membranes and curing viral proteins can realize the function of killing germs.)
