The COVID pandemic—and in much of the country, smoke-filled air caused by rampant wildfires—has renewed interest in a formerly sleepy sector of the gadget universe: the air purifier. For those of us in California, air purifiers have been essential companions in the fall months, helping to rid the unyielding stench of wood smoke from the air while (we hope) protecting our health from the potential damages of inhaling toxic gasses and particles.
Updated January 3, 2021 to add our Zigma Smart Aerio review. This smallish air purifier is adequate for smaller spaces, but it has the annoying trait of emitting loud beeps every time you push one one of its buttons to change settings, even when you’re making changes via the app, and that includes when you put it in “sleep” mode.
But do air purifiers do any good? A well-publicized Consumer Reports story from 2003 found that they were not only basically useless, but that many models produced unhealthy levels of ozone instead of removing it. The upshot was that some purifiers could make health conditions like asthma worse, not better. The Sharper Image, whose Ionic Breeze product was the poster child for air purifiers at the time, sued the magazine for libel—and lost—going out of business soon after. The air purifier had suddenly become a pariah.
In recent years, however, the EPA has reported that the typical air quality indoors (where we spend about 90 percent of our time) is much worse than it is outside, with some airborne pollutants two to five times more concentrated in the home than outdoors. These pollutants include combustion byproducts, pet dander, mold, pesticides, ozone, natural gasses like radon, and the all-encompassing category of volatile organic compounds (VOCs), which include everything from formaldehyde to trichloroethylene to chloroform. (These gasses can be 10 times higher indoors than outdoors.)
And none of this stuff is healthy to breathe.
The good news is that air purifiers have come a long way since 2003 (even Consumer Reports is back on board), though there’s still plenty of confusion out there. (Purifier manufacturer Molekule was recently hit with multiple class action lawsuits alleging its devices, which cost up to $1,049, don’t actually do anything.)
Do air purifiers protect you? The experts (including the EPA) say that HEPA (High Efficiency Particulate Air) filters are effective at reducing airborne contaminants of all types—including viruses—but are careful to note that on their own they are not enough to protect you from viruses and bacteria, and that you should still be practicing the standard battery of safeguards even if you have a great purifier on hand. That said, a purifier won’t hurt, and they are also effective at reducing (but not eliminating) indoor pollution.
At TechHive, we generally focus our air purifier coverage on smart devices; models that have some level of app support and wireless connectivity. While we don’t have the facilities to scientifically test the pollution-reduction claims of each purifier, we do report on the manufacturers’ specifications on that front, and you’ll find some guidance regarding those claims in our “what to look for” section, below.
This infomercial staple is a monster at 27 pounds and more than two feet in height, and while it won’t win any design awards, it gets the job done. Its CADR ratings of 332 to 369 are untouchable, and its battery of four filters are indeed effective at scrubbing the air clean of anything in short order. Even a lunchtime fish fry is no match for the OxyPure, which leaves the kitchen smelling as fresh as cleaning day in a matter of minutes. If the OxyPure has a downfall, it’s its app, which is simply a recreation of its onboard controls and lacks a scheduling system or any kind of pollutant monitoring view. That said, when I want my air cleaned up and I want it cleaned up fast, this is my go-to purifier.
At less than a third the price of the NuWave OxyPure, the Coway Airmega 150 is the perfect device to clean smaller spaces, with a HEPA H13 filter and a separate deodorizer to scrub offending smells out of the air. Its CADR ratings of 138 to 219 are competitive with more expensive filters like the Mila, but the petite, 12-pound device won’t make much of a dent on your décor. The only catch? There’s no app control whatsoever, so smart home enthusiasts will find this solution wanting. Still, it’s an excellent value for its capabilities.
What to look for in an air purifier
Outside of our commentary on the smart features of these purifiers that you’ll find in our individual reviews, here’s a guide to some of the key operational features in the category. You might also want to check out our buyers’ guide to stand-alone air-quality monitors, which can keep you informed of the quality of air inside your home. Since most air purifiers are best deployed in a single room, you can easily move a less-expensive air quality monitor from room to room to track the quality of all the indoor air you breathe.
Room size supported: Every manufacturer reports the size of the room its purifier is designed for, although this can be a bit arbitrary. Still, the manufacturer’s number is a good starting point. Place the purifier in a room that’s too large and it simply won’t be able to effectively clean the air.
Filter type: HEPA filters are largely standard, as are carbon filters (which are primarily used to remove foul odors from the air). But not every purifier relies on HEPA, and HEPA filters come in a variety of performance levels that correspond to their effectiveness at capturing very small particles, ranging from HEPA H10 to HEPA H14. That said, many filters don’t report this information. We’ve asked and reported where we have heard back. Higher HEPA ratings are better.
Filter lifespan: How long until you need to replace the filter, and how much do replacements cost? Some purifiers track filter life inside their app, which is helpful.
Loudness: At high air-flow levels, purifiers can be extremely noisy (and impossible to sleep near). That said, most are nearly silent at their lowest operating levels and some have special “night modes” that keep things ultra-quiet.
CADR: Clean Air Delivery Rate, a standard developed by the Association of Home Appliance Manufacturers, is represented as a series of figures that express how much air a purifier can clean in a set amount of time. Separate ratings are included for smoke, pollen, and dust. AHAM recommends that a purifier be used in a room with a size in square feet equal to 150 percent the CADR (assuming an eight-foot ceiling). (In other words, to clean a 450-square-foot room, you need a CADR rating of at least 300.) Many manufacturers claim their purifiers support much larger rooms than this, however. Note also that CADR is intended to be measured in cubic feet/minute, but some vendors measure it in cubic meters/hour. Where necessary, we have converted these figures to U.S. customary units.
Pollutant levels reported in app: What does the app tell you about your air quality? A detailed look at various pollutants is more useful than a broad “good/fair/poor” air quality rating.
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Christopher Null is a veteran technology and business journalist. He contributes regularly to TechHive, PCWorld, and Wired, and operates the websites Drinkhacker and Film Racket. Disclosure: He also writes for Hewlett-Packad's marketing website TechBeacon.