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The Best Air Purifiers, According to Doctors and Air-Quality Experts

Photo: Honeywell

With climate change, devastating wildfires that have become the norm in some parts of the world, and the weakening of environmental regulations on pollution, it makes sense that you’d be concerned about what’s in the air you breathe every day. And while you may think you’re safe if you just stay inside, according to Michele Ann Cassalia, director of marketing at the Asthma and Allergy Foundation of America (AAFA), “the indoor level of pollutants can be two to five times higher than the outdoor levels.” Along with simple methods like keeping rooms well ventilated and removing sources of pollutants where possible, an air purifier can go a long way toward improving your air quality.

Regarding the wildfires currently burning up and down the West Coast, Roger Maxfield, a pulmonologist and professor of medicine at Columbia University Irving Medical Center, says there are gases and particles in smoke that can cause irritation and inflammation in the lungs, especially for people with preexisting respiratory conditions. If you are in an area affected by wildfire smoke, first make sure your doors and windows are tightly closed. Reza Ronaghi, a pulmonologist at the UCLA Health Santa Monica Medical Center, advises sealing any gaps or cracks with old clothes or duct tape. Robert Gillio, a pulmonary critical-care physician, says for best results you’ll want your air purifier “running 24/7 at the highest speed possible to clean as much air as possible without the noise being disruptive.” Family physician William Lang, chief medical officer at WorldClinic and former director of the White House Medical Unit, stresses replacing your purifier’s filters regularly. He also points out that, because air purifiers only reduce the concentration of smoke particles — not remove them entirely — in areas with dense smoke, the concentration may still be too high with a purifier, and you may have to consider relocating.

When looking for a purifier, don’t trust claims that it can kill the coronavirus. High-efficiency particulate air (HEPA) filters, which are currently considered the gold standard in the industry, are certified by the U.S. Department of Energy to eliminate 99.97 percent of particles as small as 0.3 microns, which, according to Asriani M. Chiu, a pediatric allergy and immunology specialist at the Medical College of Wisconsin, includes mold and animal dander. Virus particles, however, are much smaller — around 0.1 microns — and won’t be trapped by HEPA filters. Some brands, like Molekule, use a newer type of filter: photo-electrochemical oxidation (PECO), which supposedly filters down to 0.1 microns, but its efficacy has yet to be proved. “It’s hard to measure how effective PECO is, since most air-quality sensors can’t detect pollutants that small,” says Vera Kozyr, the co-founder and CEO of air-pollution tracker Atmotube. In fact, Consumer Reports — which doctors including allergists Clifford Bassett and Ronald Saff tell us they trust for air-purifier testing — gave Molekule a failing grade. Your best bet, Lang says, is to look for purifiers with UV light, which “may be beneficial for killing viruses and other microbes [but] will not affect the filtration of the actual particles.”

Then there are the everyday, non-apocalyptic allergy triggers to consider. “We’ve seen many examples in homes and offices where small changes like new furniture, air fresheners, cooking, [or] cleaning significantly impact the health of the air around you,” says Nic Barnes, chief marketing officer for the air-monitor company Awair. We asked experts about what to look for when shopping for an air purifier and which models have proved to be the best.

In general, experts prefer HEPA filters over electronic or ionizing devices that release ozone into the air, which can actually irritate asthma symptoms. As Kozyr explains, ionizing filters work by releasing negatively charged ions that “stick [to] small air pollutants like bacteria and viruses, forming heavier particles that eventually fall down onto surfaces.” She explains that this can even exacerbate the spread of diseases like COVID-19 because, “in the end, you don’t get many pathogens in the air, but instead, you are surrounded by contaminated surfaces where the virus can survive for some period of time.” According to the Environmental Protection Agency, true HEPA filters have also been shown to cause small improvements in cardiovascular and respiratory health, as well as a reduction in asthma and allergy symptoms in scientific studies.

The Rabbit Air HEPA purifier comes recommended by Barnes (who likes that it filters both fine dust and volatile organic compounds, or VOCs) and by Cassalia, who notes that it has been certified by the AAFA as asthma and allergy friendly based on third-party testing performed and reviewed by the foundation and the independent certification company Allergy Standards Limited. Along with the particle-catching HEPA filter, an activated-carbon layer absorbs dangerous gaseous compounds in the air. Mitchell Grayson, an AAFA advisor and a physician-scientist specializing in pediatric allergy, asthma, and immunology at Nationwide Children’s Hospital, says carbon filters are best for eliminating smoke odors. This low-profile Rabbit Air purifier can either stand on its own or be mounted on a wall, and it includes an air-quality indicator. A light sensor automatically transitions to a lower power (read: quieter) mode when it’s time for bed.

HEPA filters are also judged by their clean-air delivery rates (CADR), i.e., the rates at which they remove allergens and other particles from the air. The Association of Home Appliance Manufacturers (AHAM) measures the CADR for different devices, which determines the interior spaces they’re capable of cleaning. Destry Washburn, a pulmonologist with Riverside University Health System, says you may need multiple filters for larger homes, so keep the square footage of your home (and individual rooms) in mind when choosing an air purifier.

For a little more, you can get a Wi-Fi-enabled Rabbit Air. This model’s connected app lets you check your room’s air quality, set the purifier to a daily schedule, set reminders to replace your filter, and more.

Certified as asthma and allergy friendly, Dyson’s air purifier can function as both a fan and a heater. It connects to the Dyson app so you can monitor air quality and control the device remotely, and it responds to voice-activated commands via Amazon Alexa.

If you don’t need the heating function, you can save on this less expensive tower-fan model. It also connects to the Dyson app for air-quality monitoring and uses an AAFA-approved HEPA filter. The fan can be set to ten different speeds, and with no moving blades, it’s safer around small children and pets than a standard fan is.

If your budget is under $300, you can’t go wrong with a true HEPA air purifier from Honeywell. The HPA250 is certified by the AHAM for rooms up to 310 square feet, while the smaller HPA5100 will work in any room up to 175 square feet. Both include a carbon prefilter to catch gaseous VOCs, and they’ve been proven during testing not to release any hazardous ozone.

For rooms up to 310 square feet, the AAFA-certified Samsung Cube offers whisper-quiet air filtering, along with high-end features like an alert that tells you when to change your filter and a smartphone app that lets you monitor your home’s air quality and control the purifier remotely. Built-in lasers constantly monitor the air quality by measuring the size and number of surrounding particles.

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The Best Air Purifiers, According to Air-Quality Experts