Air Purifiers May Not Prevent COVID-19, Experts Say

As people move indoors during cold winter weather, a growing number of air purifiers are being promoted by manufacturers as a way to combat COVID-19. But some experts say that you shouldn’t count on these gadgets to prevent catching the virus. 

Last week, ActivePure filed an application with the FDA for approval to use its air purifiers against the virus that causes covid-19. You can buy an air purifier for less than $50, although some range into the hundreds of dollars.

Some devices features HEPA filters that are certified to capture 99.97 percent of particles that are 0.3 microns in diameter, but they also capture smaller and larger particles more efficiently. The virus that causes COVID-19 is about 0.12 microns.

"A purifier is not going to eliminate all the particles or capture viruses that have landed on surfaces in the room," Dr. Abe Malkin, founder of the health service Concierge MD, said in an email interview. "A purifier is a great investment, but if someone in your household is sick, he or she should be isolated in a separate room, ideally with an air purifier."

Remove, Not Kill

The goal of most purifiers is not to kill airborne viruses but to remove them, explains Ian Cull, the owner of the air quality consulting firm Indoor Science said in an email interview. Their usefulness is a function of their "clean air delivery rate," a metric that takes into account the volume of air that the device cleans, he said.

"These products are useful in reducing risk to aerosol (or 'airborne') transmission, but they will not have a benefit for large droplet transmission (for which mask-wearing and distance work nicely) and fomite/touch transmission (for which handwashing and disinfecting high-touch surfaces work nicely)," Cull added. "So air cleaners must be viewed as a good strategy for just one of the transmission routes."

Use an air cleaner where there is a risk of aerosol transmission, Cull suggests. "For example, I won’t use one in my home unless someone has COVID," he said. "The close contact with my wife would be the most likely transmission route. But if I was to have a visitor over, a HEPA air cleaner would be a good strategy to supplement other precautions like keeping 6 feet distance and having a window open."

Active Filters to the Rescue

A more aggressive approach to air filtering is with 'active' filters. It’s important to make the distinction between air purifiers and air disinfection units, Joe Chessie, Regional Director Of Operations at the environmental safety firm VB Enviro, said in an email interview. "Air purifiers utilize filters to disinfect whereas air disinfection units utilize either a physical or chemical kill," he added.

One manufacturer of an active filtering device is Aerus, which recently announced lab results claiming that its technology can kill the virus which causes COVID-19. ActivePure uses free oxygen and water molecules and converts them into oxidizers that are released back into the room. 

Another active filtration manufacturer, The PYURE Company, claims that its products reduce SARS-CoV-2, the virus that causes COVID-19, in the air by 99% in 20 minutes. The PYURE devices disperse organic oxidants throughout the space to sanitize both the air and surfaces.

"Even the most effective air purifiers that can kill 99.9% of COVID-19 virus within minutes will not prevent the disease," Dr. Connie Araps, Chief Scientist for PYURE, said in an email interview. "But, it will minimize the amount of virus in the air and the risk of infection. Systems that can run safely all the time at these high kill rate levels should be effective at minimizing viral infection."   

Air purifiers may not be the cure-all for the coronavirus pandemic that some manufacturers make them out to be. But they can’t hurt, and the technology is sure to improve n the coming years.