Now that everyone’s staying home to avoid coronavirus, indoor air quality has become more important than ever. Many people have turned to air purifiers to cleanse the air of dust, pollen, pet dander, smoke, cooking fumes and more.
These popular home appliances even claim to scrub the air of flu and common cold germs. But can they do the same for coronavirus?
It’s a common question, especially among those caring for a sick family member quarantined at home, says Ted Myatt, ScD, senior consultant with Environmental Health & Engineering in Massachusetts. “The thought is that when people who are sick with coronavirus are breathing in and out, talking, sneezing, or coughing, they are generating particles that are likely to contain coronavirus,” he says.
While the larger particles are likely to fall to the ground or land on surfaces, smaller ones might remain suspended in the air, poised to potentially infect anyone who inhales them.
The official position from the Environmental Protection Agency is that no air purifier has yet been proven to protect users from the novel coronavirus, while the U.S. Centers for Disease Control and Prevention (CDC) has no formal statement on it. The Food & Drug Administration (FDA), however, has indicated that air purifiers might be useful alongside other measures.
On March 30, as part of a broader statement, the agency said, “FDA believes that certain sterilizers, disinfectant devices, and air purifiers…may help reduce this risk of viral exposure based on our current understanding of these devices and SARS-CoV-2.” SARS-CoV-2 is the scientific name for this novel strain of coronavirus. Here’s high-touch surfaces to clean and disinfect daily.
The experts we spoke with told us it definitely couldn’t hurt, as long as people understand what an air purifier can and can’t do.
Air Purifier Basics
Most purifiers have a fan that draws air through a disposable HEPA (high-efficiency particulate air) filter, which can trap more than 99 percent of contaminants that are three-tenths of a micron. (A micron is one-millionth of a meter. For comparison, a human hair is about 60 to 120 microns.) The coronavirus, at a little more than one-tenth of a micron, might seem likely to slither past the filter.
But Myatt explains that particle physics isn’t so cut and dried. “A HEPA filter actually does a much better job of capturing particles that are both larger and smaller than three-tenths of a micron, which is the hardest size to capture,” he says. “The smaller particles move in random order and get bumped around by larger particles.” Eventually, he says, they get pulled into the filter.
What’s in a Sneeze?
Even if the coronavirus’s size somehow allowed it to elude capture, it’s important to remember that no one coughs or sneezes out a single virus particle. “You’re expelling respiratory secretions that have viruses in them,” along with proteins and other cellular debris, Myatt says. “Those particles are definitely big enough to be captured by a HEPA filter.” This is how often you should replace these seven filters at home.
As scientists scramble to find a treatment for COVID-19, little reporting has been done on the use of air purifiers. However, research has shown air purifiers to be effective against other airborne diseases.
“Two studies show that air filtration can reduce the risk of measles and flu,” says Dr. Kullar. “The same thing is true with SARS,” or severe acute respiratory syndrome, a disease caused by another type of coronavirus that spread rapidly in 2003 and is the illness most comparable with COVID-19. “The CDC recommended using HEPA purifiers with SARS,” she says. “We can probably make similar recommendations for COVID-19 eventually.”
Richard Corsi, dean of the Maseeh College of Engineering and Computer Science at Portland State University is cautioning that people should not rely on purifiers to entertain guests, “having people into your home for a meal or perhaps staying several days is a big concern as the holidays approach. Some may have been exposed; others don’t even know that they are infected.”
Corsi emphasizes that people should not stop wearing a mask or washing their hands just because they have a purifier. “Don’t let your guard down. A purifier may lower the level of particles in the air, but it doesn’t eliminate the risk,” Corsi says.
A Novel Approach
At least one brand of air purifier uses a different technology. Molekule uses a process called photoelectrochemical oxidation, or PECO, “which destroys pollutants rather than just capturing them,” according to company spokeswoman Stephanie Borman.
The technology uses ultraviolet light to produce free radicals, a type of molecule that destroys air pollutants, presumably including viruses. Company officials stated in March that they planned to test their device against the new coronavirus. So far, no results have been released.
Go With the Flow
If you decide to try an air purifier with a HEPA filter, be sure to select the right size for the space where your sick family member is quarantined. Manufacturers make this easy by listing the appropriate room dimensions on the packaging for each unit. They also list the clean air delivery rate, or CADR, which reflects how many times per hour clean air is exchanged in a room.
“Your goal is to have air circulate in a space multiple times an hour to increase the likelihood that virus particles enter the airflow of a filter,” notes Erin Sorrell, Ph.D, an epidemiologist at Georgetown University. Consumer Reports recommends a minimum CADR of 240, which exchanges the air in a room five times per hour. Examples include the Honeywell HPA300 True HEPA Allergen Remover and the Blueair Blue Pure 211+.
Don’t overlook the benefits of low tech. Opening a window in an enclosed room, if weather permits, can help with ventilation even if you’re using an air purifier. “[It] can help move air throughout a space and encourage [virus] particles to drop,” Sorrell says.
The placement of the air purifier is important. “If it’s way over in the corner behind the curtains, it’s not going to be as effective as if it’s near the bed,” says Dr. Myatt. “It’s best to have it within a few feet of where the person is sleeping or spending most of their time so it can pull in any air or respiratory secretions they exhale.”
Joseph Allen, director of the Healthy Buildings program at the Harvard T.H. Chan School of Public Health recommends, “situatuating your purifier in the center of the room, at least three feet away from walls and corners and elevated on a stool or table. You also need to set it on the highest setting, and, yes, it will probably be somewhat noisy.”
Exercise Caution When Replacing Filters
Experts also recommend handling the filter with caution, since coronavirus can survive on select hard surfaces for days. “When you take it out, wear a mask, use gloves and bag the filter and throw it away, so it’s not releasing any particles,” Dr. Myatt advises.
Just One Tool
Dr. Kullar emphasizes that while an air purifier may be an important tool in protecting your home and family from coronavirus, it should never be considered the first line of defense. “Follow social distancing guidelines, wear a face covering, wash hands frequently and treat high-touch surfaces with disinfectants.” Find out the four household products that kill the coronavirus, according to Consumer Reports.
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