What are the misconceptions about HEPA filters on the market and is HEPA filter technology reliable?

The market has a strong influence onHEPA filterWhat are the misconceptions?HEPA filterIs the technology reliable?

The core components of the air purifier are the fan and filter, HEPA filter can be called the heart of the air purifier, directly affecting the performance and service life of the air purifier. The simple principle is that the fan sucks the air in, the HEPA filter filters out dust, pollen and other particles such as PM2.5 and other fine pollutants, similar to the activated charcoal filter can also remove the implication. The air blown out in this way is "clean air".

First of all, from the principle of understanding HEPA filters for particles with a diameter of 0.3 microns or more removal efficiency can reach 99.97% or more, is the most effective filtration medium for smoke, dust and bacteria and other pollutants. But many people on the HEPA filter will produce some misconceptions that the smaller the particles the more difficult to remove, the larger the particles HEPA filter filtration effect is better.

1、Misunderstanding of HEPA filters

In fact, HEPA is relying on the van der Waals force between fine particulate matter and solids to work, it is very good for the filtration efficiency of particles above 0.5 micron and below 0.1 micron, the smaller the particles the smaller the inertia, the larger the particles the larger the inertia, so the filtration effect will also be better. But the purifier affects the amount of dust suction by two factors consisting of a HEPA filter and wind volume, some filters the higher the filtration effect, the wind received a greater boost, clean out of the air volume will also be reduced, through such a boost, the best natural filtration effect will be reduced. In practice it is not the smaller the particles the more difficult to get rid of, but according to the density of the HEPA filter not used to determine the effect of filtering size particles. For example, some filters, when the particles are less than 1um, but the smaller the easier to get rid of. That's why there are different sizes of HEPA filters on the market, and the price of the purifier is different.

2, HEPA filter main material

There are a variety of materials that make up HEPA, which can be divided into PET filter paper, PP (polypropylene) high-efficiency filter paper, PET and PP are composite high-efficiency filter paper and glass fiber high-efficiency filter paper. Among them, PP (polypropylene) is paper, generally can not be washed. The other part of the HEPA filter is made of PET or PTFE, which is the origin of many online claimed to be washed HEPA filters, however, here I must suggest that the efficiency of PET is very low.

As just described, the higher the efficiency of the HEPA filter, the higher the resistance, the less the actual ventilation of the purifier will be. With less airflow, the number of purifications per unit of time will also decrease, and the CADR value will decrease.

Extended Reading:

Analysis of the reliability of HEPA filter technology

1. Does HEPA represent absolute high efficiency purification ability?

Filter air purifiers are one of the most common and widespread in the purification market, and HEPA filters are the most effective filtration material in filter air purifiers. The word "HEPA" is broken down into - High, Efficiency, Particulate, Airfilt, (air filtration device). So "HEPA" is often a reference for consumers looking for efficient air purification. But what is the truth? In the air purifier market, filters that use the name "HEPA-type", "HEPA-like", or "99%HEPA", are all The name "HEPA-type", "HEPA-like" or "99%HEPA" filters have not passed the leakage test of high-efficiency filters - DOP method.

In addition, the HEPA standard is set by the U.S. Department of Energy and states that it is more effective in filtering particles with a particle size of 0.3 μm (microns). However, the DOP test can't really test the filtration effect of HEPA filters on particles below 0.3 microns, but 90% particles in the air, including bacteria, viruses, etc., are smaller than 0.3 microns, and the smaller the particle size of these hazards, the more harmful they are to human health.

2. Why does the true purification efficiency of HEPA filters decrease?

Analyze several reasons together:

① The purifier itself has a seal;

② The design of the purifier itself;

(iii) Leakage from the edges around the filter material;

④ Leakage between the filter element and the housing

⑤ After 6 months of filter use, the actual efficiency of the filter at this time will be reduced by 50% in an ordinary polluted environment, according to the CDC testing and recommendation report;

(6) The more purification levels a purifier has, the more power it will consume and the stronger the wind speed and noise will be

(vii) The influence of the environment itself (temperature, humidity, etc.);

⑧ Depending on the severity of air pollution, the buildup of pollutants on the HEPA filter varies;

⑨ It is affected by the wind speed of the purifier, which is ineffective in terms of purification efficiency when the wind speed is slow, and there are problems such as noise and cold air when the wind speed is fast.

All of the above reasons basically cause the actual filtration efficiency of HEPA filters to decrease, so even if the filtration efficiency of the filters themselves really reaches over 99%, it doesn't mean that the actual purification rate of the filtered air purifiers is also over 99%. And it has been proven that most HEPA filter air purifiers are much less purifying. Especially for the filter material around the edge of the leakage, or the filter element and the shell between the leakage of factors, coupled with the HEPA material itself specifications, grade, etc., which has an important impact on the final purification effect of the filter air purifier, but also make its purification effect has another layer of uncertainty.

3. How big is the O&M cost burden of HEPA filter air purifiers at a later stage?

It must be affirmed that HEPA is truly capable of removing airborne particles, but due to its high capture efficiency, it can easily become ineffective due to excessive dust accumulation. In actual use, it is necessary to constantly clean and replace the filter to maintain its purification effect. But this is too much for the family, such a late operation and maintenance costs are too great, the frequent replacement of accessories alone will quickly exceed the price of the air purifier itself when purchased.

The current market price of HEPA filters is between 400-700 yuan. If the pollution like Beijing and serious cities, according to the air quality inspection experts 3 months at least once to replace the filter recommendations, home filter air purifier replacement HEPA filter yearly expenditure of at least about 1200 yuan.

And the filter air purifier in the maintenance needs extra attention, if you can not regularly clean or cleaning method is not appropriate, the filter of dust and harmful substances will be through the cycle, re-released into the indoor air and cause secondary pollution. So whether it is for the impact of environmental pollution, or its own air purification efficiency, HEPA filter air purifier in the long-term operation, the actual role is not as high as described by the producers, but in the late stage of the occurrence of some relatively difficult trouble.