In terms of operating principles, air purifiers generally fall into three categories: passive, active, and hybrid (combining both passive and active methods).
Regarding the technologies used to remove airborne particulate matter, the main methods include mechanical filtration, electret filtration, high-voltage electrostatic precipitation, and negative ion or plasma-based methods.
Mechanical Filtration
Particles are typically captured via four mechanisms: direct interception, inertial impaction, Brownian diffusion, and the sieving effect. While effective at collecting fine particles, this method creates significant airflow resistance; achieving high purification efficiency requires dense filters, which results in a shorter lifespan and necessitates regular replacement.
High-Voltage Electrostatic Precipitation
This method uses a high-voltage electrostatic field to ionize the air, charging dust particles so they are attracted to and collected on an electrode. Although airflow resistance is low, the method is less effective at capturing larger particles and fibers. It can cause electrical discharge, is time-consuming and troublesome to clean, and tends to generate ozone, leading to secondary pollution.
Electret Filtration
While standard mechanical filtration is effective for particles larger than 10 microns, capturing particles in the 5-micron, 2-micron, or even sub-micron range using high-efficiency mechanical systems becomes expensive and significantly increases airflow resistance. Electret air filtration materials achieve high capture efficiency with low energy consumption, combining this with the low airflow resistance characteristic of electrostatic precipitation. Crucially, they do not require an external high-voltage power supply (tens of thousands of volts), so they do not generate ozone; furthermore, being made of polypropylene, they are easy to dispose of.
Electrostatic Dust Collection
This method can filter out dust, smoke, and bacteria smaller than human cells, helping to prevent conditions such as lung disease, lung cancer, and liver cancer. The most harmful airborne particles are those smaller than 2.5 microns, as they can penetrate cells and enter the bloodstream. Standard purifiers using filter paper to trap dust are prone to clogging; the accumulated dust not only fails to provide sterilization but also easily causes secondary pollution.
Electrostatic Sterilization
Utilizing a high-voltage electrostatic field of approximately 6,000 volts, this method instantly and completely eliminates bacteria and viruses adhering to dust particles, thereby helping to prevent illnesses such as the common cold and infectious diseases. The sterilization mechanism involves disrupting the four polypeptide chains of the bacterial capsid protein and damaging the RNA.
