Whether we are buying an air purifier or a fresh air system, we will hear the merchant mention "HEPA filter", but many people still don't know about the HEPA filter. They only know that it is an "advanced filter". Let's have a chat with everyone to talk about the HEPA filter and see what it is.
What is a HEPA filter?
The HEPA filter is also called HEPA high-efficiency particulate filter. The English name is High-efficiency particulate arrestance. It is usually made of polypropylene or other composite materials. HEPA filter is an internationally recognized and best high-efficiency filter material. Originally used in nuclear energy research and protection, HEPA is now widely used in high-purity places such as precision laboratories, pharmaceutical production, atomic research and surgery.
How HEPA filters work
HEPA filters are filtered in four forms: interception, gravity, airflow and van der Waals force
1. Interception mechanism is a commonly understood sieve. Generally, large particles of 5μm and 10μm are intercepted and sieved.
2. Under the influence of gravity, the dust particles with small density and high density will decrease in speed after HEPA, and will settle on the HEPA filter net like sediment sinking on the bottom of the river.
3. The filter mesh is unevenly woven to form a large number of air vortices, and the small particles are adsorbed on the HEPA filter screen by the air cyclone.
4. The ultrafine particles do Brownian motion and impact the HEPA fiber layer, which is purified by the influence of van der Waals force. A viral carrier such as less than 0.3 μm is purified under the influence of this force.
What is the single filtration rate of the HEPA filter?
HEPA is a high efficiency air filter. Calculated according to the single filtration rate, the standard HEPA filter can filter particles as small as 0.3 microns in air, and the filtration rate is at least 99.97%. It is widely used in hospitals, laboratories and precision instrument production workshops where air quality is critical. .
The single filtration rate refers to the filtration capacity of the filter by comparing the change in the amount of air particles in a single process of taking in air from the filter to discharging fresh air.
HEPA filter rating
According to the EU EN1882 standard, according to the high efficiency of filtration, we divide the HEPAl filter into five grades: coarse filter, medium efficiency filter, sub-high efficiency filter, HEPA high efficiency filter and ultra-efficient filter. A sieve having a particle filtration efficiency of more than 99.9% for a particle size of 0.3 μm is referred to as H12.
The national standard requires that the filtration efficiency of HEPA materials be above F9. However, as the grade rises, the stronger the purification ability, the greater the wind resistance. Therefore, the higher the HEPA rating under the same conditions, the lower the CADR value of the air purifier.
How often does the HEPA filter change?
The core indicator for judging the service life of the filter is the dust holding capacity. The core data affecting the dust holding capacity is the expansion area of the filter screen. The larger the expansion area of the filter screen, the higher the dust holding capacity and the more durable the filter screen. The dust holding capacity refers to the amount of dust accumulated when the resistance reaches a predetermined value (generally 2 times the initial resistance) due to dust accumulation under a certain air volume. (If you feel too much trouble, under normal circumstances, the HEPA filter can be used for 6-12 months, according to the local air quality.)
Why is it sour?
In fact, this is a problem with most filter air purifiers.
Because the air purifier is working, it will adsorb particles and microorganisms in the air on the filter screen. Under the proper temperature and humidity, the filter will breed bacteria and produce odor. In addition, the activated carbon filter in the air purifier also produces a sour taste after being damp.
In response to this situation, the small editor of Shiyang Electromechanical recommends that the filter element be taken out and placed in a place where the sun is ventilated, and the "sour taste" may become lighter. If it does not work, we recommend that you replace the filter directly.
Can the HEPA filter be washed?
Replacing the filter element is the most straightforward approach, but a friend is concerned that the cost of replacing the filter element is too high. Indeed, HEPA filters for air purifiers range in price from 200-1000 yuan. There are many kinds of materials that make up the HEPA filter. It can be divided into PP (polypropylene) high-efficiency filter paper, PET filter paper, PP and PET composite high-efficiency filter paper and glass fiber high-efficiency filter paper. Among them, PP (polypropylene) is paper, so it is generally not washable.
Another part of the HEPA filter is made of PET or PTFE, which is why many online claims to wash the HEPA filter. However, such HEPA filters are inefficient and are not recommended.