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.
Do Air Purifiers Work?
Yes—to an extent. As the Environmental Protection Agency (EPA) notes, while they are effective at cleaning the air and reducing air pollution, they cannot remove all pollutants.
OK, So *How* Do Air Purifiers 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?
Can Air Purifiers Help with Wildfire Smoke?
Yes. The EPA recommends using a portable air cleaner and/or high-efficiency HVAC filter when the air quality is poor in your area due to wildfire smoke, with the caveat that it should be the right size for your room (more on that below) and should not produce ozone. You'll also want to make sure it can filter out particles 2.5 micometers or smaller, like the models suggested at the end of this story.
If you're in a bind or cannot afford an air purifier, the EPA also offers a tutorial on creating a DIY one using an air filter, a box fan and duct tape or bungee cords. (Though they also say this should not be a permanent solution, and there are concerns that the fan could overheat, posing a safety hazard, so if you pursue this option, please keep an eye on it.)
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 or smoke particles from the air (the EPA recommends models that remove particles less than 1 micron in diameter). With that in mind, we rounded up four top-reviewed ones that all meet the criteria below.