Air purification devices usually consist of a motor, fan, and air filter. The motor and fan work to circulate the air, while the filter works to remove contaminants from the air as it passes through the unit. In addition, some air filters use negative ion generators that attract airborne particles and successfully remove them from the atmosphere.
What methods are used in air filtration?
There are many methods used to filter and deliver purified air. Listed below are the most popular methods:
Mechanical filtration using fiber media
The most widely used method of air purification, mechanical filtration systems remove contaminating particles such as dust, dust mites and pollen from the air by trapping them in a fiber filter for removal.
HEPA filters, or high efficiency particulate filters, are the most efficient type of mechanical air filter and should remove at least 99.95% of airborne particles from the environment.
These filters work by using the process of electromagnetism, passing polluted air through an ionization section to draw in pollutants and trap them for removal. They work on a similar principle to magnets. As positive and negative charges are attracted to each other, this process adds an electrical charge to the particles, which are then trapped and stored on an oppositely charged flat plate for removal. In the case of electrostatic air filters, there is no filter media because charged plates are used instead.
Not all air pollutants are particles. There are also gaseous pollutants such as molecules from combustion processes, including gas stoves, car exhaust and tobacco smoke. The air can also contain volatile organic compounds (VOCs) such as cleaning fluids, adhesives, paints, and varnishes. To remove these molecules, you need a specialized air filter designed to remove gaseous pollutants.
Photocatalysis is another method of removing gaseous pollutants. Instead of using adsorbent media, photocatalytic air purifiers use ultraviolet light and a catalyst – usually titanium dioxide – to clean the air.
In this process, the ultraviolet light charges the catalyst, which then targets harmful pollutants and effectively destroys them.
The plasma method uses a high voltage current to ionize the air and charge the molecules in the air. This creates reactive radicals that then attack and destroy air pollutants.