What are the classifications of the working principle of air purifiers?

       What are the classifications of the working principle of air purifiers?
　　 The working principle of the air purifier is relatively simple, that is, a filter screen and a fan, suck indoor dirty air into a closed air purifier, filter out impurities in the air through layers of filters, leaving clean air to be blown into the room again. Circulate several times, knowing that the air is clean. At present, the air purification form can be roughly divided into three categories: passive filtration (filter filter, such as olive green air purifier), active filtration (ionic filtration, such as Bianang air purifier) and combined filtration of the two (such as Sharp Plasmacluster) group).The main technologies are as follows:
　　 Filter type. This type of air purifier uses porous filter materials to trap and collect particles suspended in the air. It generally uses HEPA filter or activated carbon filter, which can filter tiny particles and adsorb harmful gases such as formaldehyde, benzene, and ammonia. If the indoor air is not particularly dirty, based on the average use of 6-8 hours a day, the service life of activated carbon is only about 6 months, and the filter element must be replaced. Now most of the purifiers also have indicator lights to replace the filter element. If it is not replaced in time, the purifier will not function as it should. In addition, this type of purifier generally has multiple layers of filtration. Be careful not to install the filter in reverse after maintenance, otherwise it will affect the purification effect and reduce the service life.
　　 Electrostatic type. The electrostatic air purifier has a high voltage of thousands of volts inside, which can charge particles through ionization and then be adsorbed. Therefore, for such products, be sure to check the product's certification certificate or the conformity inspection report issued by the National Household Appliances Quality Supervision and Inspection Center to avoid danger due to unqualified product quality. Under normal circumstances, the dust collecting plate of this type of air purifier is It is a relatively sharp metal piece, which is easy to scratch when cleaning. It is not recommended for the elderly.
　　 Photocatalyst type. Since the photocatalyst can only act as a catalyst and does not participate in the chemical reaction itself, the effect of the photocatalyst air purifier is relatively long-lasting. Such products are more convenient to clean and maintain, and can be used by middle-aged and elderly people. Since the photocatalyst must be catalyzed by light to produce a reaction, when using it, do not cover the photocatalyst material or the light source designed to irradiate the material.
　　 Negative ion type. The negative ion device generates a certain amount of ozone while generating negative ions. If the ozone concentration is too high, it may be harmful to health. Therefore, the air purifier with negative ion function should pay attention to the ozone concentration generated by the machine should not be too high. One is to smell with the nose, if the pungent odor is very heavy, it means that the ozone concentration may exceed the standard; the second is to check whether the inspection report is qualified. People with a history of allergies should avoid using such products as much as possible.
　　 Ultraviolet type. Excessive ultraviolet rays can cause photochemical reactions, which can cause a series of changes in human body functions, especially to the skin, eyes, and immune system. Therefore, when using such products, be careful that there should be no ultraviolet light leakage, that is, you can't see the lamp tube exposed, so as not to cause harm.