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As the world continues to experience the ebbs and flows of COVID-19 and new variants arise, you’re likely looking for any science-backed tool to protect yourself from the coronavirus. This may be particularly true if you’re immunocompromised and may not have garnered a robust immune response from the COVID-19 vaccine.
One of the tools that has been consistently shown to lower transmission rates of COVID-19 is proper air filtration. In a new study published in the U.S. Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report, researchers placed four respiratory simulators in a 584-square foot conference room. One of the simulators was exhaling infectious particles, while the other three were not. This was meat to mimic someone with COVID-19 sharing the same space with uninfected individuals.
Researchers then placed two high efficiency particulate air (HEPA) cleaners in the conference room, which reduced aerosol exposure by up to 65 percent. When masks were worn and HEPA filters were used, exposure was reduced by up to 90 percent.
“Ventilation is a well-established method for reducing potential exposures to infectious aerosols,” note the study’s authors. “One recommended option, especially when existing HVAC systems might be insufficient, is adding portable HEPA air cleaners to rooms. The results of this study support the use of portable HEPA air cleaners to reduce exposure to airborne particles.” HVAC systems are heating, ventilation, and air conditioning systems.
For most experts, this isn’t unexpected news. After all, the SARS-CoV-2 virus that causes COVID-19 is approximately 0.125 micron (125 nanometers) in diameter. That’s within the particle size range that HEPA filters can capture: 0.01 micron (10 nanometers) and above, reports Wirecutter. Still, it’s reassuring to have further scientific evidence that air filtration can play a role in COVID-19 prevention.
“The results of this study don’t surprise me in the slightest, which is a good thing,” says Brent Stephens, PhD, Professor and Chair of the Department of Civil, Architectural, and Environmental Engineering at the Illinois Institute of Technology, who was not involved with the study. “It’s nice to see quantitative, measured impacts on a topic we know would be true.”
The research echoes the results of a May 2021 observational study from the Morbidity and Mortality Weekly Report, in which researchers analyzed COVID-19 mitigation efforts and transmission in Georgia elementary schools from November to December 2020.
The incidence of COVID-19 was 37 percent lower in schools that required teachers and staff to wear masks and 39 percent lower in schools that improved ventilation. The ventilation improvement strategies included dilution methods (35 percent lower incidence of COVID-19) or a combination of dilution and filtration methods (48 percent lower incidence). “Dilution methods” means tactics like opening windows and doors and using fans.
Overall, the data supporting the use of air filtration is likely most useful for event spaces, businesses, and offices. It doesn’t necessarily mean you need to buy HEPA filters for your home.
“If you’re in your own home, you’re worried more about visitors or occupants whose exposure you can’t control, and there are other ways to deal with that,” says .
Even so, people with compromised immune systems may benefit from — or be comforted by — the extra layer of protection when it comes to mitigating not only COVID-19, but other airborne viruses like the flu, which may return in a big way following the pandemic.
“With appropriate layers of protection, maybe normalcy can return to your life to some degree,” says Dr. Stephens. “One layer might be a mask, another could be social distancing, another could be air filtration, and yet another layer is ventilation. Those are all additive, such that you keep increasing your protection.”
And of course, the most important layer: getting vaccinated to protect yourself and those around you.
General Benefits of Air Filters
Although there are more immediate steps you can take to reduce the risk of COVID-19 in your home (asking guests if they’ve been vaccinated, avoiding gatherings with unvaccinated friends and family, practicing good hand hygiene, etc.), you may enjoy some general health benefits of air purifiers.
Air purifiers tend to be good at filtering dust, smoke, and pollen from the air, according to Consumer Reports. Research on room air purifiers has shown that HEPA filters can reduce particulate matter by 50 percent or more — and coarse particles like dust by 30 percent.
Still, it’s uncertain how that directly affects health generally. Nearly a dozen studies have shown improved heart health among people who use air purifiers, and an EPA review of eight studies found modest improvements in at least one area of health, like allergies. Other research shows air filtration can reduce clinic visits in people with asthma.
But with most research, it’s difficult to definitively link the use of air purifiers to specific health benefits since reported improvements have been inconsistent and more long-term studies are needed, notes Consumer Reports. Some research also involves other variables that can affect outcomes, like regular vacuum cleaning, keeping pets out of the bedroom, and using pillow covers.
“If anything is exacerbated by a pollutant or suite of pollutants, then it can be addressed to some degree with ventilation,” says Dr. Stephens. “But air filtration is additive. What happens in most buildings is there’s a minimum level of ventilation to dilute indoor sources of pollutants, and then filters can scrub the air, too.”
All of this said, if you’re encouraged by the potential health benefits of air filters and want to give them a try yourself, here are a few top models recommended by Wirecutter. You can also check out air purifier reviews from Consumer Reports.
Winix AM90 ($190, Amazon)
The contemporary design of this air filter is appealing, and you can control it using an app on your smartphone. It has a washable fine mesh pre-filter for the largest airborne particles, an activated carbon filter to reduce odors, a HEPA filter, and air-cleaning technology to neutralize bacteria and viruses.
Coway AP-1512HH Mighty ($230, Amazon)
A good option for bedrooms and living rooms, this was one of the best-performing and most durable purifiers tested by Wirecutter. Within 30 minutes, it reduced heavy smoke pollution in a 135-square-foot New York office by up to 99.6 percent. You can shut off its display lights, which makes it a good option if it’ll be near your bed.
Austin Air HealthMate HM400 ($715, Austin Air)
Its large 15-pound VOC filter (VOCs are volatile organic compounds, or more broadly known as odors) outperformed others tested by a wide margin and its HEPA filter provided excellent performance on particulates. That said, this one is much more of a splurge than other air filters.
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Air Purifier Buying Guide. Consumer Reports. April 21, 2021. https://www.consumerreports.org/cro/air-purifiers/buying-guide/index.htm.
Gettings J, et al. Mask Use and Ventilation Improvements to Reduce COVID-19 Incidence in Elementary Schools — Georgia, November 16–December 11, 2020. Morbidity and Mortality Weekly Report. May 28, 2021. doi: http://doi.org/10.15585/mmwr.mm7021e1.
Heffernan T. The Best Air Purifier. Wirecutter. April 8, 2021. https://www.nytimes.com/wirecutter/reviews/best-air-purifier/.
Interview with Brent Stephens, PhD, professor and Chair of the Department of Civil, Architectural, and Environmental Engineering at the Illinois Institute of Technology
Lindsley WG, et al. Efficacy of Portable Air Cleaners and Masking for Reducing Indoor Exposure to Simulated Exhaled SARS-CoV-2 Aerosols — United States, 2021. Morbidity and Mortality Weekly Report. July 9, 2021. doi: http://doi.org/10.15585/mmwr.mm7027e1.