The coronavirus has, for now, changed the way we approach our day-to-day lives. Some nonessential shops are closed, kids have been learning how to do their schoolwork from home, and social distancing has become a household term. Unfortunately, it seems like the end of this pandemic is still quite a ways off. As people seek to protect themselves and their families, technology is one place they look to for answers.

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Since COVID-19 is transferred from person to person and can be airborne, you might think an air purifier could reduce exposure. It’s not that simple, however.

Can an air purifier protect you from the coronavirus?

No, it can’t.

An air purifier can combat other causes of respiratory problems and improve the overall air quality in your home, but a standard HEPA filter can’t capture and destroy something as small as a virus. Even if the virus is captured, it would likely survive for some time.

A PECO filter might make a difference, but only in a limited way. The method PECO filters use to pull particles from the air can catch incredibly small items. According to Dr. Mariea Snell, assistant director of the online doctor of nursing program at Maryville University, “a PECO filter could remove a virus from the air given its size,” but she goes on to add that “it’s not likely this will make a large impact, considering [coronavirus] lives on surfaces for an extended period of time.”

The coronavirus is spread by person-to-person contact and coming into contact with contaminated surfaces. The best option for combating the coronavirus is to avoid contact with anyone that may be infected and use strong hygiene practices. Wash your hands often, and wear a properly rated facial mask in places where you might be exposed to the illness.

Understanding the science of air purifiers and viruses

Air purifiers use fans to draw in air and pass it through a filter before expelling the purified air out the other side. They’re particularly effective at removing odors and large particulates from the air. If you suffer from pet allergies, for example, an air purifier can help capture the dander and reduce your symptoms. On the other hand, there is a limit to what an air purifier can capture.

Even the most powerful air purifiers can only capture particles as small as 0.1 microns or larger, and the vast majority of air purifiers will only capture particles 0.3 microns or larger. A micron is a unit of measurement equal to one-millionth of a meter, sometimes called a micrometer.

The primary culprits of poor indoor air quality are larger than this size limit; mold, pollen, and pet dander are all larger and can be caught and eliminated by a standard HEPA filter. A slight margin of error is why air purifiers claim an effectiveness rate of 99%.

Viruses are roughly 100 times smaller than bacteria, and typically range from 0.004 to 0.1 microns in size. This means even the most powerful air filters would struggle to purge a virus from the air.

COVID-19 belongs to a family of viruses known as coronaviruses. The 2013 SARS epidemic was also caused by a coronavirus, which was 0.1 microns in size. According to Snell, the size of COVID-19 is approximately 0.125 microns.

Alen Corp, the company behind one of Digital Trends’ best air purifiers of 2020, recommended using a filter treated with an antimicrobial coating that’s claimed to kill mold, mildew, fungus, bacteria, and viruses on contact.

You definitely want to make sure that you are regularly replacing the filters.

We also spoke with Molekule co-founder and co-CEO Dilip Goswami. “Molekule’s PECO technology has been shown to destroy airborne viruses, and we’ve conducted extensive testing on RNA-type and DNA-type viruses to demonstrate that,” he said, adding that the company is “currently working with the University of Minnesota to test the technology on a strain of coronavirus.”

While Goswami’s claims are promising, the company has endured harsh reviews from Wirecutter and Consumer Reports within the last year. Digital Trends hasn’t tested Molekule’s air purifier.

Finally, we reached out to Dyson. According to a representative, Dyson air purifiers will capture viruses, but won’t destroy them. The virus will remain alive inside the filter for as long as it typically survives.

As multiple scientific studies have shown, viruses can lie dormant for extremely long periods. Dyson went on to comment: “You definitely want to make sure that you are regularly replacing the filters … .”

HEPA vs. PECO filters

There are two primary types of air filters: HEPA and PECO. HEPA is an acronym for “high-efficiency particulate air.” PECO stands for “Photo Electrochemical Oxidation.”

HEPA filters are made out of a type of fabric that functions similar to a net. Air is passed through the fabric by a fan. Particulates are caught by this fabric, while the now-clean air is allowed to exit out the other side. Over time, the particles will accumulate on the fabric until it loses efficiency. That’s why filters have to be replaced.

PECO filters work in a similar, but more complex way. First, air passes through a sort of “pre-filter” that’s laced with carbon. Next, it moves through a larger filter that captures and binds molecules to ions and then destroys them.

HEPA filters are not much more effective than medium-efficiency air filters.

Which is better? We asked Patrick Van Deventer, product manager for Trane indoor air quality products. “According to the Environmental Protection Agency (EPA), HEPA filters are not much more effective than medium-efficiency air filters with a MERV [Minimum Efficiency Reporting Value] rating between 7 and 13,” said Deventer.

“They are also highly restrictive and thus have a limited air delivery, so they are typically used in smaller appliances such as portable air cleaners and not in central ducted HVAC systems.” A MERV rating refers to a scale that measures how powerful your air filter is.

Michael Rubino, indoor air quality expert and president of All American Restoration, added more caveats. “There are air purification technologies that can destroy biological contaminants such as mold spores and viruses (such as H1N1 and SARS),” he said. “However, the technology is not just HEPA; air purifiers that utilize photocatalytic oxidation (PCO) release ions into the air that bind to these contaminants and destroy them. There are certain air purifiers that utilize filtration in addition to PCO, such as Air Oasis iAdapt Air.”

A final note. We’ve discussed consumer-grade air purifiers here, but industrial air purifiers capable of completely cleaning the air do exist. However, these machines are large and routinely cost more than $1,500 (sometimes, much more).

MERV-13 filters

According to the National Air Filter Association, a MERV-13 filter is able to remove 90% of particles between 3 and 10 microns in size, 85% of particles between 1 and 3 microns in size, and 50% of particles between 0.30 and 1 microns in size.

So, in theory, a MERV-13 filter might be able to filter viruses out of the air, depending on the specific virus. It is important to keep in mind that a MERV-13 filter only removes 50% of those particles from the air, so it is by no means a foolproof method and should not be viewed as such. What it is, however, is a step toward more efficient consumer-grade air filters.

Many advertisements hail the MERV-13 filter as a way to stop viruses, but the truth is more nuanced. While it may be able to stop some viruses, it won’t stop them all, and there is no confirmed evidence that it can stop the spread of the coronavirus. Investing in a MERV-13 filter will improve your indoor air quality and greatly reduce the number of allergens in the air, but it should not be viewed as a safeguard against disease.

The fundamental problem

Even the best air purifier doesn’t solve the fundamental problem; like most viruses, the coronavirus is spread by person-to-person contact and contact with contaminated surfaces. Air purifiers are capable of filtering the air in a room over time, but viruses tend to travel short distances between people or land and linger on surfaces. An air purifier, even one equipped to kill a virus, will often fail to catch a virus before it comes into contact with a person or surface.

Air purifiers are still great to have year-round. Coronavirus isn’t the only concern, as this year’s awful pollen season has proven. An air purifier can help reduce the impact of pollen and seasonal allergies, eliminating sniffles and putting trees in their place.

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