Air purifiers may reduce the risk of coronavirus infection

Exhaled air and micro-droplets of saliva can contain viruses that remain in the air for several hours. Because of them, people can pick up the disease while in a room with infected people. Therefore, air purifiers play a rather important role in the fight against the spread of coronavirus: they remove viruses from the air, thereby significantly reducing the risk of infection. These devices pass the air in the room through small filters, and viruses and bacteria are no longer released back – at least in some cases …

How well air purifiers rid a room of viruses and bacteria depends on several factors. To find out, in 2020, scientists from Germany (University of the Bundeswehr) conducted a whole study.

In a test in an 80 square meter room, the air purifier was able to halve the viral load within six minutes. It was a purifier that itself filters out aerosol with particles with a particle diameter of 0.1 to 0.3 microns by 99.995%.

The scientists used a highly efficient air purifier with a HEPA filter H14 in the experiment. Such filters are available, for example, in the industrial model TAC 750 E. It passes a very small amount of viruses.

“A significant advantage of indoor air purifiers is that they provide a low viral load and you don’t have to constantly open windows to air out. Air purifiers will be especially useful in offices and schools, as well as in waiting rooms, canteens, recreation rooms and shops. Accordingly, in those places where a lot of people gather together and talk, and where it is difficult to ventilate the room often and thoroughly,” the authors of the study explain.

The results of the study also show that the efficiency of the filter is highly dependent on the volume of air that it needs to clean. For large rooms, particularly powerful devices are needed that can filter a large volume of air per hour.

The location of the air purifier also matters a lot, with experts suggesting a performance decrease of around 20 percent depending on location. For example, lamps and other heating elements can interfere with airflow, so it is not recommended to install the purifier near them.

By the way, the filters do not need to be constantly replaced: when comparing the results of the new filters and the used ones, scientists could not find a significant difference. Therefore, experts suggest that the filter can be used for several years – of course, cleaning it, but not replacing it. Some modern devices are equipped with a rather useful filter heating function: if you use heating up to 100 ° C for half an hour every day, this will help “kill” the viruses that have got into the purifier.

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Purifier or sterilizer?

Air purification is most often understood as the fight against natural pollutants: dust, odors … Until recently, disinfection was used mainly in medical institutions. But after the start of the coronavirus pandemic, “medical” technologies began to be actively used in household devices. Now, in addition to mechanical filters, air is passed through ozonizers, treated with ultraviolet light, photocatalysis is used … One of the progressive technologies in the fight against viruses has become air disinfection by low-temperature plasma.

Don’t be intimidated by the name: low-temperature plasma is essentially an ionized gas at room temperature (about 30-40°C). Under its influence, the cell membrane of viruses and bacteria becomes vulnerable, plasma particles react with DNA or RNA and destroy it. In this way, bacteria and viruses are destroyed not only in the air, but also on surfaces – in addition, the technology allows you to disinfect water, food, decompose allergens… Since the 90s, the technology has been used in the sterilization of surgical equipment, as it is the most effective in this direction.

But there are only a few household devices based on cold plasma technology: for example, INTECH Technologies has launched a compact Plazmabox on the market, which is capable of eliminating up to 99.9% of viruses and bacteria on an area of ​​10 m2 and more advanced Plazmatech, designed for areas up to 40 m2 and having one of the largest cleaning radii among sterilizers and air purifiers.

Which is more effective in the fight against coronavirus: an air purifier or ventilation?

Isn’t there enough ventilation to “kick” viruses out into the street? In principle, ventilation can also reduce the viral load in a room when it comes to cross-ventilation – when open windows are opposite each other. But ventilation cannot seriously reduce the viral load, because sometimes the rooms do not have windows at all (for example, in the corridor) or the windows are not located opposite each other. In addition, for example, in large rooms, windows will have to be kept open for a very long time.

Many buildings have a built-in ventilation system. However, experts say, unlike an air purifier, it can create the risk that viruses will not be filtered, but rather spread through ventilation shafts. Therefore, air purifiers are superior to ventilation systems in terms of efficiency. By the way, the purifier is worth buying for other reasons: they are good at removing dust mites, unpleasant odors and pollen from the air and thus provide a better indoor climate.

However, air purifiers do not replace protective masks. Because there is still a risk of contracting the coronavirus if your interlocutor is sick, and when talking with him you do not keep your distance.

What filters trap viruses

H14 filters are the best at fighting viruses – they are found mainly in high-performance air purifiers used in enterprises. But how good are lower standard HEPA filters?

Basically, HEPA 13 filters are found in cheaper devices for home use. Even weaker filters are HEPA H7 (they filter out 99 percent of viruses, not 99.995 percent). To remove half of the aerosols from the air, H7 purifiers take two and a half times longer than devices with H14 filters. “Even 10-fold aerosol filtration with an H7 class filter yields a worse result than simple filtration with an H14 class filter,” the scientists write in their study.

We advise you to choose a model with a high filter class, although the lack of efficiency of a weaker filter can be partially compensated by ventilation.

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