Air purifier HEPA filter rating

 From the perspective of whether a single purification effect is clean or not, the higher the HEPA filter level, the better! From the research data, the single purification efficiency of H11 grade HEPA filter is 98%, while the single purification efficiency of H12 grade HEPA filter can reach 99.9%. The higher the grade, the higher the purification efficiency and the better the purification effect. . 

For home use, there is no need to pursue high levels blindly, just the ones that are suitable! 1. What is a HEPA filter? The filters of air purifiers can generally be divided into three categories. They are the basic primary filter, which can filter out large-size solid particles in the air, while the HEPA high-efficiency filter is the second category, and its main function is to filter out The small-size solid particles that cannot be filtered out by the primary filter, such as PM 2.5, etc., play the role of secondary purification. The third type of filter is an activated carbon filter, which mainly relies on activated carbon to adsorb formaldehyde, toluene and other toxic chemicals in the air to improve air quality. 2. How to purchase air purifiers (1) HEPA high-efficiency filter The higher the HEPA high-efficiency filter, the more complex the filter structure, the finer the size of the particles that can be purified, and the deeper and cleaner the purification effect. The higher the level of HEPA high-efficiency filter, the more expensive the configuration. Generally speaking, HEPA filters above H11 can effectively purify common air pollutants such as PM 2.5, and the price is relatively moderate. It is the most popular household HEPA filter. Friends in areas with frequent smog can buy H12 HEPA high-efficiency filters, which have higher purification efficiency and higher cost performance to prevent smog.

At present, many consumers are prone to fall into a misunderstanding when buying air purifiers: the higher the filter level, the better. For this reason, it is necessary to reshape the correct concept about the filter grade. First of all, we need to explain the H13 concept abused by many businesses. In fact, H13 comes from the European standard EN1822-a rule that is completely biased towards high resistance glass fiber. The mainstream filter materials used in air purifiers on the market today, such as Toray, 3M, domestic filters, and Korean filters, are all electret polypropylene materials, which mainly rely on electret electric fields to adsorb particles. If EN1822 is mandatory For certification, it is necessary to remove the electret treatment according to EN1822 Appendix B, then the original H13 filter will immediately shrink to F8 or even lower. So strictly speaking, if the manufacturer advertises the use of "3M's H13 filter", it is incorrect. In fact, the electret technology greatly improves the filtering performance of the filter screen for fine particles, and can make the polypropylene fiber filter with extremely low resistance reach the H13 level of EN1822 filtration effect (that is, the filtration efficiency for the most easily permeable particles More than 99.95% under the rated air volume). Basically, all air purifiers on the market are using electret technology, which is completely beneficial to consumers and air purifiers. However, it was obliterated by the ruthless EN1822. 

All in all, EN1822 is a standard that applies to clean rooms and ventilation systems. This standard has a persistent demand for single-pass filtration efficiency. It does not allow single-pass filtration efficiency to be reduced, but it is very tolerant of resistance. However, it is a pity that EN1822 does not It is not suitable for household air purifiers that emphasize the number of cycles and filter resistance, and it is not the standard implemented in the air purifier industry. Ironically, the term "H13" in such a standard has become a conventional concept-although everyone in the industry knows that in strict accordance with EN1822, the so-called "H13" of polypropylene filters is not the real 谷歌代投. In fact, if you really use H13's old-fashioned glass fiber filter paper, consumers will suffer. The air purifier at home will become a behemoth. The power consumption will discourage consumers, the noise will make people unable to sleep, and the purification effect will be greatly reduced. The purifier industry will regress to the distant glass fiber era. Another thing to note is: According to EN1822, the filter level is actually linked to the rated air volume, because the greater the air volume, the lower the filtration efficiency. For example, a Swiss brand declares that its filter is H12/H13. Its maximum air volume is only 440m3/h, so if we change the fan to make the air purifier's air volume reach 880m3/h, can its filter still reach the H13 level? It’s impossible, because as the wind speed increases, The filtration efficiency will be lower than 99.95%. Also according to this logic, when the rated wind speed is low enough, some filtration efficiency without 99.95% filter can also claim to reach the H13 standard at high wind speeds. Therefore, as a consumer, it is important to understand that the filter level is not a constant constant, and it is meaningless to talk about the filter level without the air volume (the air volume is linked to the CADR, which will be discussed later). Under the current national conditions, consumers' "correct understanding" of H13 should be: the filter paper used in this high-efficiency filter has a filtration efficiency of more than 99.95% for 0.3 micron particles at a wind speed of 5.33 cm per second (H12 is 99.5%) . Our discussion below should be based on this understanding. 

Now we can return to the question that everyone is most concerned about, whether the higher the filter level, the better. The answer is no. Why? This goes back to another essential question: what exactly is the air purifier doing? It's simple: Inhale V cubic meters of air per unit time and intercept a part of the particles. We assume that the intercepted part accounts for X% of the total, and finally discharge the filtered air. How many micrograms of particles are collected by the air purifier per unit time? (Assuming that the concentration of particulate matter in the air is constant at C micrograms per cubic meter.) The calculation is as follows: the mass of particles inhaled by the air purifier per unit time M = C * V * X% micrograms. It is easy to understand that the larger the M, the stronger the capacity of the ultra hepa air purifier. Among them, the H13 grade filter has X=99.95%, and the H12 grade filter has X=99.5%. But don't forget, V hasn't counted yet. Consumers only care about X, but often ignore V. On the same machine, the larger X is, the smaller V is. Assuming that the V of the H13 filter is 100 cubic meters per hour, the V of the H12 filter may be as high as 150 cubic meters per hour. Then the mass of particles collected per unit time of the air purifier equipped with H13 filter M=C*100*99.95%=99.95C then the mass of particles collected per unit time of the air purifier equipped with H12 filter M=C*150*99.5 %=149.25 So obviously, in this case, the air purifier equipped with the H12 filter performs better than the H13. Therefore, a responsible manufacturer should consider when V*X is equal to the maximum value. In fact, V*X is the CADR under the ideal model, that is, the clean air output rate. 

Its physical meaning is also very simple to understand. Inhalation per unit time V volume air, the filtration efficiency is X%, which is equivalent to the production of V*X% volume of completely pure air (of course, the original air volume of V*(1-X%) is also produced, and the sum of the two air volumes is just right. Equal to V, conserved) But sadly, most manufacturers consider: saving the cost of educating consumers, one-sided emphasis on X and ignorance of X*V. In the end, consumers accepted the one-sided notion that the bigger the X, the better. But it is not seen that as X slightly increases, V will decrease sharply, resulting in a sharp decrease in V*X (ie, a decrease in CADR).

 In the imperial capital where PM2.5 has always exceeded the standard, even if it is equipped with a filter with 100% filtration efficiency (H13 is only 99.95%), if the V is not large, the PM2.5 in the room will always be at a high level, no matter how long it will not decrease. Because the purification speed can't keep up with the intrusion speed of foreign particles. Reasonable consumers will eventually find that the standards for air purifiers, whether it is the AHAM (American Household Appliance Manufacturers Association) standard or the Chinese national standard, put CADR (that is, the size of X*V) in the first place. . In other words, a high level of the filter is not enough, a high level of the filter and a large air volume V are really good. Many seo排名公司 pursue the maximization of X and sacrifice V, such as those that one-sidedly emphasize the "H13" grade filter and completely ignore CADR. Representative works: a Swiss brand. Of course there are also X machines that are not considered at all. So what are the consequences of not considering X at all? The lifespan is short, and yes, X is related to lifespan. The representative work is a Japanese brand, a machine donated 5 folded filter paper, known as one year to replace one, can be used for 5 years. In fact, 5 of them will be down every year. In addition, there is a Swedish brand that does not even put activated carbon in order to obtain super high CADR, so I won't repeat it. To say a little off topic, the life span is not only related to X, but also obviously related to the unfolded area of ​​the filter paper. 

It is easy to understand that the larger the unfolded area of ​​the filter paper, the more particles it can carry. You can calculate the price per square meter of filter paper and then make a judgment when calculating whether the filter is cost-effective. In summary, the selection of the filter grade should essentially be a balance of many factors. It's not that the higher the wishful thinking, the better, or the lower the better.