Best and Worst Air Purifiers of 2021

We've tested dozens of models. Some blew us away, while others simply blew it.

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overhead shot of 6 air purifiers grouped together
A collection of air purifiers awaiting testing in CR's lab.
Photo: Stephen Yang

If you’re allergic to pollen, autumn—the peak of ragweed season and the reintroduction of mold spores from fallen leaves—can be both a beautiful time of year and an ugly reminder that seasonal allergies have the propensity to stifle your fun.

Closing your windows can help keep some of those outdoor agitators at bay, but indoor pollutants, such as dust and mold, are ever-present in our living spaces. Without fresh air cycling through your home, air pollution indoors can reach concentrations five times higher than outdoors, according to the Environmental Protection Agency. A good air purifier can reduce some of those pollutants and help you breathe easier.

“The best air purifiers we’ve tested are able to remove small particles from your air whether at high or low speed,” says Misha Kollontai, who oversees testing of air purifiers at CR. “They are able to do so at a relatively low noise level, which is great since they are operating around the clock.”

On the flip side, Kollontai observes that the worst air purifiers on our list struggle to clean the air on both low and high speeds, adding, “Oftentimes, poor performance in removing particles like smoke and dust is accompanied by a lot of noise, which can be bothersome in a living area.”

To test air purifiers, we inject smoke and dust particles into a sealed chamber and measure how well each model removes particles between 0.1 and 1 micron. (Human hair has a diameter of 100 microns.) We use a particle counter to measure the change in particle concentration as the air purifier runs for 15 minutes at the highest speed, and then at a lower speed. And because these run day and night, we measure noise levels, in decibels, at every speed, and calculate annual operating costs for filter replacements and energy use to run the machine 24 hours a day.

The three top models in our air purifier ratings earn an Excellent or Very Good rating for particle reduction at a low speed while keeping noise to a minimum. (They all aced the high-speed test, as do many models.)

Here’s a closer look at the three best air purifiers we tested, followed by the three worst. They’re listed alphabetically.

CR’s take: With the recent addition of the Alen BreatheSmart 75i Pure to CR’s ratings, there’s a new reigning champ in the air purifier space. The 75i proves to be top-notch at capturing and removing dust and smoke while running at its highest and lowest levels, earning an Excellent score in both tests. Holding a conversation or getting work done while the unit runs should be easy enough, as the model receives a "Good" score for noise levels on high and low speeds. Another reason this model receives high marks? Its energy and operating costs, including filter replacements, run roughly $140 annually, which is significantly less than the two other standout Blueair models on the list. And it covers up to 1,300 sq. feet, which is more than double the Blueair 211+ and significantly more than the Blueair Classic 605.

CR’s take: The Blue Pure 211+ is one of only three models that earns Excellent scores for particle removal at both the high- and low-speed settings. It’s not as quiet as the top-rated model at the high-speed setting, but its score is on par with most of our recommended models. It’s roughly half the price of our No. 1 air purifier, but its annual costs are still around $195 for filters and energy use. It’s rated for rooms up to a claimed 540 square feet, but it can be a pain to move from room to room because the 16-pound machine doesn’t have a carrying handle or wheels. A light will flash when it’s time to change the filter, and this model also has a machine-washable fabric prefilter (a stocking that slips over the bottom half of the machine and comes in five colors) for capturing larger particles, like pet hair, thus prolonging the life of the main filter.

CR’s take: Man, can this machine clear a room. It’s one of only three models that earns Excellent scores for particle removal at both the high- and low-speed settings. It runs whisper-quiet at low speeds, but it’s noisy on high speed. It’ll clean the air quickly, but you won’t want to be in the room while it does, especially if you’re having a conversation or watching TV. Of course you pay for all that performance. It’s one of the most expensive air purifiers in our ratings, and that’s just the initial cost; filter replacements and energy use will set you back around $225 per year. The machine weighs a hefty 30 pounds but has casters that make it easy to cart from room to room. It’s claimed capacity is a room of 775 square feet.

CR’s take: The Molekule Air won followers through an aggressive social media campaign touting a patented PECO filter, which the maker claims will destroy airborne pollutants at the nanoscale level. CR didn’t test those claims, but in our tests for particle reduction, the machine wasn’t able to adequately clean the air in the room. The Molekule Air earns a Poor score in our test for particle removal at low speed and receives a Fair rating at high speed. So while we can’t say whether the company’s proprietary PECO technology destroys gases, viruses, and mold, we can say with certainty that the appliance falls short in its ability to reduce airborne particle pollution. For that you pay $800, plus almost $180 per year to run it. Molekule says the purifier can handle rooms up to 600 square feet. But based on our calculated rate of cleaning, we wouldn’t put this machine in any room larger than 100 square feet.

Find out whether the Molekule Air lives up to the hype.

CR’s take: This is a case of “you get what you pay for.” The lowest-ranking air purifier in our ratings happens to carry the lowest retail price. Much like the Zone Halo, below, Pure Enrichment claims the Pure Zone Mini 2-in-1 removes close to 98 percent of dust and smoke, but when put to the test, the unit fails to live up to that. It earns a Poor rating for dust and smoke removal on both the lowest and highest settings. Conveniently, the Mini 2-in-1 is both portable and rechargeable. That means it can be turned on in your car or on a plane, as demonstrated on the product’s website. This helps lend itself to an Excellent rating for energy output and the cheapest operating cost—$29 annually—of all the air purifiers on our list, but with such poor results, it’s not much more than a white noise machine.

CR’s take: Pure Enrichment claims that its Zone Halo model cleans the air of nearly 98 percent of dust and smoke in rooms of up to 100 square feet, but when put to the test, we found that even on its highest speed, this unit earns just a Fair rating on removing dust and a Poor rating for removing smoke. At its lowest speed the Halo earns Poor scores for both dust and smoke removal. Though it’s relatively quiet and earns an Excellent score for energy output, its ineffectiveness makes these qualities feel like moot points.

For more on air purifiers and how to pick the right model for your home, check our air purifier ratings and buying guide.

Headshot of CRO Home Editor Tanya Christian

Tanya A. Christian

I've spent more than a decade covering lifestyle, news, and policy. At Consumer Reports, I'm happy to sit at the intersection of these specialties, writing about appliances, product safety and advocacy, consumer fairness, and the best tools and products to help you spruce up your home. When I'm not putting pen to paper, I'm exploring new cultures through travel and taking on home makeover projects, one room at a time.