The coronavirus, officially known as COVID-19, has become a serious health concern across the globe. The majority of the deaths have been limited to mainland China, but new clusters have appeared in South Korea and Italy. The Centers for Disease Control and Prevention (CDC) warn that the virus will likely start spreading in the United States. With a rising infection and mortality rate, people are taking steps to protect themselves from exposure in whatever way they can.
Since COVID-19 is transferred from person-to-person and can be airborne, you might think an air purifier could reduce exposure. Unfortunately, it’s not that simple.
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’ll 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. Snell, “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. That slight margin of error is why air purifiers claim an effective 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 Dr. Mariea Snell, Assistant Director of the Online Doctor of Nursing Program at Maryville University, 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 anti-microbial coating 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’s 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.” Goswami added 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 (who wished to remain unnamed), Dyson air purifiers will capture viruses, but won’t destroy them. The virus will remain alive inside the filter for as long as the virus survives.
As multiple scientific studies have shown, viruses can lie dormant for extremely long periods of time. Dyson went on to comment, “You definitely want to make sure that you are regularly replacing the filters and as long as you purchase a Dyson purifier you can feel confident that you are doing the best you can do to keep your air as clean as possible.”
HEPA versus PECO filters
There are two primary types of air filters: HEPA and PECO. HEPA is an acronym for “High, Efficiency, Particulate, Air.” On the other hand, 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 EPA, HEPA filters are not much more effective than medium efficiency air filters with a MERV 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 system.” For reference, a MERV rating refers to the Minimum Efficiency Reporting Value, a scale that measures how powerful your air filter is.
Michael Rubino, President and an indoor air quality expert with 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 & 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).
Still, 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 if equipped to kill a virus, will often fail to catch a virus before it comes into contact with a person or surface.