Nowadays, there’re varieties of air-purification techniques in the market, all of which has their benefits and drawbacks. Let’s have a general overview:
1. HEPA physical filtration
With high effective filters (mainly HEPA filters) intercepting particles in the air, HEPA physical filtration is the most effective and reliable technique. It can intercept 99.7% particles of 0.1μm and over 99.97% particles of 0.3μm (1/200 of the diameter of hair). HEPA acts as a effective filtration of tiny pollutants such as smoke, dust and bacteria, and it can keep the indoor PM2.5 density under 1μg, even to several thousandths of one μg. Despite its effectiveness, HEPA is costly as its filters needs frequent change to prevent secondary pollution.
2. ESP (electro static precipitator) dust collection
ESP not only eliminates particulate pollutants in the air, such as dusts, coal smoke, pollen, cigarette smoke and kitchen fumes, but also releases trace amount of ozone, which sterilizes and dissolve formaldehyde in the air. In addition, its working resistance is much less than HEPA filtration and its energy consumption can be as low as several watts. Moreover, its filters only needs regular washing, which saves the huge cost of filter replacement. However, low quality ESP equipment generates excessive ozone, which is harmful to your health.
3. (active carbon) absorption filtration
As a porous carbonaceous material, active carbon has a large surface to filter the air and absorb particles, so it has a good filtration effect. But absorption filtration only works well under low-pollutant conditions, and its absorption effects reduces as its service continues. When absorbing serious formaldehyde or benzene, its service life can only last 5 or 6 months. Overused active carbon filters will release pollutants into the air at high temperatures, which will affect the filtration effect. The filters need regular replacing, which is also a high cost.
4. PCO (Photo Catalytic Oxidation)
PCO is the most effective biochemical purification technique, and it has a great effect. Exposed in ultraviolet rays, PCO oxidation-reduction reaction emerges on the surface of photocatalyst, and it can produce high-oxidable free hydroxyls, which oxidate various organics and some inorganics. It breaks the cytomembranes of bacteria and proteins that solidify virus. It also decomposes organic pollutants such as formaldehyde and xylene into water and carbon dioxide and achieve instant sterilization. However, the purification effects is highly correlated with pollutants and its contact time, wind power and photocatalyst surface. Misuse of PCO purifiers might produce excessive ozone.
All these main air-purification techniques above has its own benefits and drawbacks. However, air-purifiers and ventilation systems nowadays combine several of the techniques above to meet different using conditions. For users, we need to analyze specific using conditions and compare different air-purification techniques to make the best of the advantages and avoid the disadvantages.