Does secondary pollution from air purifiers really exist?

Pollution can be seen everywhere in modern society, especially in some big cities. Car exhaust, factory emissions, etc., plus other gases emitted by people in their daily lives, have greatly reduced the air quality, and the number of people suffering from illness is really increasing. Taking this situation into consideration, researchers have developed a new generation of air purifiers, which are basically a must-have for every household. So, is secondary pollution caused by air purifiers true?

Living in a modern urban environment where air quality is declining and pollution index is rising, people are particularly concerned about the health hazards caused by air pollutants such as haze and PM2.5. As people continue to pursue better quality of life, air purifiers have gradually entered ordinary people's homes, especially in big cities with poor air quality, where air purifiers have almost become a common household appliance. In Beijing, air purifiers have become a must-have product in many homes and schools, and have entered ordinary people's homes and public places like televisions and refrigerators. Some time ago, Beijing focused on discussing issues related to air purifiers in primary and secondary schools.

The birth of its products is mainly due to the increasingly serious air pollution caused by social development. Air purifiers can absorb, decompose or transform various air pollutants (generally including dust, pollen, odor, decoration pollution such as formaldehyde, bacteria, allergens, etc.), effectively improving the cleanliness of the air. Air purifiers can effectively neutralize harmful gases emitted from volatile organic compounds, formaldehyde, benzene, pesticides, mist hydrocarbons, and paints, while achieving the effect of eliminating physical discomfort caused by inhaling harmful gases. Originally used to solve indoor air pollution caused by new home renovation or other reasons, now due to the frequent visits of smog weather, citizens buy air purifiers more to prevent and filter PM2.5 that enters the room with air as well as other toxic and harmful substances in the air, such as formaldehyde, infectious bacteria, etc. I remember that decades ago, a smog outbreak in a major foreign city caused a lot of population losses. The main reason was the large number of viruses carried by the smog in the air, which caused the widespread spread of diseases.

Can you sit back and relax with an air purifier? The answer is no, because the air purifiers currently sold on the market mainly use filter filtration, that is, physical purification technology (HEPA for short) with HEPA filter (dry filter composed of laminated borosilicate microfibers) as the carrier. Most of the air purifiers on the market use HEPA technology. This is a physical purification technology that uses filters as the main purification medium. Air purifiers manufactured under HEPA technology use purely physical materials, such as melt-blown cotton that looks like cotton paper, to intercept dust and bacteria. The interception node is the filter. Over time, the filter becomes a gathering place for bacteria and pathogens. Coupled with the cultivation of the indoor environment, it is easy to cause secondary pollution and create a larger source of pollution. Therefore, secondary pollution is also an urgent problem that practitioners in the air purification industry need to solve.

Recently I heard that there is another kind of purification on the market. The polluted air goes through six purification steps including microcrystalline activated carbon, water curtain purification, molecular complexation purification, nano-photocatalytic purification, ultraviolet purification, and negative ion purification, and finally discharges clean air. The harmful substances filtered by microcrystalline activated carbon, water curtain purification, and molecular complex purification are transferred to the ecological wetland through a circulation transfer system. Under the joint action of plants, organisms, and media, the harmful substances are decomposed and converted into plant nutrients to be absorbed by plants. It can be said that this is the purest ecological air purifier currently available.