Maybe you’ve got allergies. Maybe you’ve received one too many push notifications about the air quality in your area. Or maybe you’ve heard it can help prevent the spread of COVID-19. Whatever your reason, you’re considering getting an air purifier, but deep down, you can’t help but wonder: Do air purifiers work? They promise to filter out dust, pollen, smoke, even germs—but do they really deliver on that, or are they just overpriced fans? We pored over research and turned to Dr. Tania Elliott, an allergist and national spokesperson for the American College of Allergy, Asthma and Immunology for answers.
Do Air Purifiers Work? Yes—Now Let’s Clear the Air on Some Misconceptions
FIRST, WHAT DO AIR PURIFIERS *ACTUALLY* FILTER OUT?
Air purifiers (also known as air sanitizers or portable air cleaners) suck particles from the air, such as pollen, fungal spores, dust, pet dander, soot, bacteria and allergens. So, how do they work? The machines use a filter—or a combination of filters and UV light—to remove impurities and pollutants from the air. They’re designed to improve the air quality in a single room, and as the Environmental Protection Agency (EPA) notes, while they are effective at cleaning the air, they cannot remove all pollutants.
OK, SO HOW DO THEY WORK?
In general, air purifiers filter in one of two ways: via fibrous media air filters or electronic air cleaners. The former is kind of like a catcher’s mitt, with the particles getting scooped up in the filter. The latter—electronic air cleaners, which include electrostatic precipitators and ionizers—use electricity to charge particles and adhere them to oppositely charged plates in the machine. Some even use ultraviolet light to kill airborne microorganisms. Now, don’t you feel all Bill Nye for knowing that?
WILL AN AIR PURIFIER PROTECT ME AGAINST COVID-19 AND OTHER ILLNESSES?
The EPA and many doctors agree that air purifiers are helpful—especially if the outdoor pollution is high, or if it’s too cold to throw open your windows and let in tons of fresh air. “Viral droplets, like SarsCoV2 and the flu, these can stay suspended in the air for hours, so an air filter can't hurt, but remember the droplets can also land on surfaces and sit there as well,” explains Dr. Elliott. “An air purifier shouldn't replace mask-wearing, hand washing, isolation, not sharing personal products and sanitizing measures.” As the CDC says, consider ventilation part of a “layered strategy” to prevent the spread of the coronavirus.
DO AIR PURIFIERS *REALLY* HELP PEOPLE WITH ALLERGIES?
Yes—and they can be particularly helpful for people who suffer from pollen or pet-related allergies. “Pet allergens stay suspended in the air for months at a time, even if the pet is no longer in the home,” explains Dr. Elliott. “Air purifiers that can capture fine particulate matter are your best bet. It is also helpful for people with pollen allergy, as we inevitably track pollen into the home from our clothes, shoes and hair.” By “fine particulate matter,” she means dust, pollen, mold and the like. Particles considered “fine” are less than 10 microns in diameter (ultrafine ones, such as soot, smog and viruses, are less than 2.5). For comparison, a human hair is about 50 to 70 microns in diameter. So we’re talking small—really, really small.
Unfortunately, air purifiers “won't work for people with dust mite allergies, as dust mites are too large of a particle to remain airborne,” Dr. Elliott says. For that type of allergy, your best bet is to vacuum, dust and wash your bedding regularly, and invest in allergen-proof bed covers.
Still, many HEPA filters and air purifiers tout being able to remove particles 0.3 microns in diameter. Keep an eye out for those if you’re looking for a model that can help remove viruses from the air (the EPA recommends models that remove particles less than 1 micron in diameter). So we rounded up four top-reviewed ones that all meet the criteria below.
WHAT SHOULD I LOOK FOR IN AN AIR PURIFIER?
1. CADR (Clean-Air Delivery Rate) Rating
The Clean Air Delivery Rate (CADR) is a number you’ll find on most air purifiers’ packaging—or at least any company that voluntarily submits their machine to the Association of Home Appliance Manufacturers (AHAM). The CADR indicates the amount of clean air a purifier can produce at its highest fan speed. If the unit can successfully filter tobacco smoke, dust and pollen particles at a certain rate, the manufacturer will (typically) submit the purifier for AHAM verification.
2. AHAM (Association Of Home Appliance Manufacturers) Verified Mark
The AHAM is an organization that verifies a purifier's CADR rating through independent laboratory testing. “During testing, the air cleaners are exposed to specific quantities of tobacco smoke, dust and pollen. After the air cleaner is operated for a certain duration, the amount of each pollutant in the air is measured,” according to the official AHAM website. “The higher the CADR, the greater its ability to filter that specific pollutant. Air cleaners with HEPA filters are designed to remove 99.7 percent of airborne pollutants [that are] .3 microns and larger.” Long story short? An AHAM certification is a quick way to know the device can effectively remove smoke, dust and pollen from your home.
3. True HEPA
“High-efficiency particulate air” (HEPA) is another verification for filters defined by the U.S Department of Energy. Basically, it means that the filter can remove at least 99.97 percent of dust, pollen, mold, bacteria and any airborne particles with a size of 0.3 microns. However, it’s important to keep in mind that “there is no widely accepted definition of HEPA performance in consumer products,” according to the EPA. “They are unlikely to be equivalent in performance to HEPA-designated filter systems used in health care buildings and industrial processes, but still have very high removal efficiency (i.e., usually 99 percent or higher) for the reported particle sizes tested.”
4. Size Guidelines
“Be sure to get one that matches the size of the room by checking the CADR,” says Dr. Elliott. There’s one CADR score for pollen, one for dust and one for smoke, and the association recommends choosing a purifier with a CADR score that’s at least two-thirds of the room’s area. We know—it sounds complicated. But really, it’s just basic math: If you’re clearing the air in a 10-foot by 10-foot room, that’s 100 square feet, so you want a CADR score of at least 67 in each of those three categories.
ARE THERE ANY TYPES OF AIR PURIFIERS I SHOULD AVOID?
Yes. Stay away from ozone-generating air cleaners. As the name implies, they produce ozone, which can cause health issues in high concentrations, and the EPA reports that ozone does little to actually remove pollutants. On that note, it’s worth mentioning that no federal government agency has approved of their use in homes (though some brands may claim that). You’re better off going with an air purifier that uses a fibrous media air filter or an electric air cleaner.
Great. So What Are the Best Air Purifiers I Should Check Out?
HOW LONG DOES AN AIR PURIFIER TAKE TO CLEAR THE AIR IN A ROOM?
The short answer? Give it at least 30 minutes to an hour. Some companies recommend running it all day, every day, since pollutants are continually being tracked into the house and are wafting through open windows. (Of course, it’s worth noting the impact that doing so may have on your electricity costs.)
WHAT’S THE BEST PLACE TO PUT AN AIR PURIFIER?
Let’s be real: Air purifiers aren’t the chicest-looking additions to your décor, so it’s tempting to tuck them behind a plant or large piece of furniture. Don’t. You want to keep them in the room where you spend the most time—ideally, the room where the most vulnerable in your family (infants, elders and people with asthma) spend the most time—and in a position so that the clean air is close enough so they’ll be able to breathe it in, according to the EPA. Beyond that, it’s also worth consulting the manufacturer’s instructions for placement.
WHAT ARE OTHER WAYS I CAN IMPROVE THE AIR QUALITY IN MY HOME?
1. Keep Windows Open
While it might be less practical to crack open a window in the dead of winter, it’s important to remember how stale indoor air and heating systems can reduce air quality and increase allergy-inducing particles. “Even in the cold months, open windows from time to time to allow fresh air to move into the house. Also, move potential air contaminants out by using fans in the kitchen to remove cooking fumes,” suggests Dr. Nicholas BuSaba, associate professor of otolaryngology at Harvard Medical School, and fellows from Harvard health publishing.
2. Vacuum Often
“A clean house may be a healthier house, because good indoor hygiene can greatly cut down on dust and animal dander,” says Dr. BuSaba. “Your cleaning efforts should focus on strategies to reduce the accumulation of pet dander, mold and dust lurking in your home.” Be sure to vacuum carpets and area rugs at least once or twice a week with a vacuum cleaner equipped with a HEPA filter for best results.
3. Regularly Change Air Filters
If you have a forced-air heating system, you’ll want to make sure you’re changing the air filters every three months, according to the CDC. “In homes where the HVAC fan operation can be controlled by a thermostat, set the fan to the ‘on’ position instead of ‘auto’ when you have visitors. This allows the fan to run continuously, even if heating or air conditioning is not on,” adds the National Center for Immunization and Respiratory Diseases (NCIRD).
4. Turn on Your Exhaust Fans
Another simple method to improve your home’s air quality? Keep the exhaust fan turned on in your kitchen or bathroom. “Exhaust fans above your stovetop and in your bathroom that vent outdoors can help move air outside…Keep the exhaust fans turned on for an hour [when you can] to help remove virus particles that might be in the air,” recommends the CDC.