When people buy air purifiers, they are often confused by the various promotional slogans provided by the manufacturers. The most attractive ones are like "our purifier does not need to change the filter" or "the filter life is up to 2 years. "It’s a slogan. Many people don’t know much about the principles of air purification. They blindly pursue the long life of the filter, which leads to misunderstandings.
Air purifiers can be roughly divided into two categories: electrostatic adsorption type and filter type.
The filter type is what we usually call the filter type, which uses a large air volume and high wind pressure fan to pass the air through one or more layers of filters to filter out particulate matter and volatile organic matter. The current common way for volatile organics is to use activated carbon filters. The principle of adsorption is to adsorb volatile organic molecules through the huge surface area of activated carbon. Many people have a misunderstanding about particulate matter filtration. It is not that the pore size of the filter screen is smaller than the particulate matter and thus the particulate matter is blocked. Its main working principle is adsorption, which is why the filter screen must have a certain thickness.
For larger particles, due to their larger mass, the direction of movement is not easily changed by the airflow, and it is easier to hit the fibers in the filter during movement and be adsorbed. For smaller particles, due to their lighter weight, they are easy to change direction due to airflow or gravity during movement. There are two solutions to this situation: One is to increase the density of the filter to increase collision interception. Probability; the second is to charge the particles, thereby increasing the adsorption force. This has led to another way of air purification: electrostatic adsorption. The technology of electrostatic adsorption is very easy to understand. Simply put, a strong electric field is added to a space, and particulate matter is attracted and hits the filter. As a dust collecting plate, it is adsorbed, and it is the same principle as the electrostatic dust removal in industry. The manufacturer claims that the air purifier that does not need to change the filter is a product that uses this technology. The main disadvantage of this technology is that the filtration efficiency is generally low, and it cannot reach the 99. 9% purification efficiency, while another problem is that due to the existence of a strong electric field, the generation of ozone is also relatively large, and ozone is also an air pollutant, too high content also has an impact on the respiratory system. The specific amount of ozone released needs to be tested by a third-party agency.
As for the filtering purification method commonly used in current air purifiers, because the filter is commonly used for filtering by HEPA filter, the HEPA filter will gradually become saturated with the increase of adsorbed particles, and the dust holding rate will gradually decrease, resulting in The efficiency of the purifier decreases and the energy consumption increases. At the same time, the particulate matter adsorbed on the filter is also a hotbed of virus and bacteria, which will multiply and breed bacteria. If it is not replaced for a long time, it will not only not have the purification effect, but will also form secondary pollution and become a source of pollution. In fact, considering the domestic air quality, it is recommended that the filter should be replaced after three months of use to protect your health. The picture below shows the air purifier filter after long time use. I wonder how you feel after seeing it?