If you’re allergic to pollen, you may find some relief as outdoor temperatures drop and windows are closed for the season. Small comfort, because it's prime time for indoor pollutants, such as dust and mold.
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 tested clean the air quickly and perform well on the quieter low speeds too,” says David Trezza, CR’s lead tester for air purifiers. “The worst air purifiers struggle on high speed, barely do anything at all on low speed—and they still cost hundreds of dollars a year to maintain.”
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 on 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: The Blue Pure 211+ is one of only two models that scores Excellent for particle removal at both the high- and low-speed settings. It’s not as quiet as the top-rated model on the low-speed setting, but it’s not as noisy on the high-speed setting, either. 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 two models (along with the Blueair 211+) that scores Excellent 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 a year. The machine weighs a hefty 30 pounds but has casters that make it easy to cart room to room. It's claimed capacity is a room of 775 square feet.
CR’s take: Unlike the two Blueair models above, the Honeywell HPA300 is designed to sit on either a tabletop or the floor and has a convenient carrying handle. It weighs 17 pounds and is rated for rooms up to a claimed 465 square feet. It's among the quietest air purifiers we've tested on its highest speed, garnering a Good in that assessment. This model has a programmable timer and filter indicator lights, which tell you when it’s time to change the main filter and prefilter. The carbon prefilter needs to be replaced every three months, and the main HEPA filter needs to be replaced once a year. The cost for all those filters plus the energy required to run the machine comes out to just over $200 a year.
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 price. Hamilton Beach says this model’s filter never needs to be replaced (just vacuumed periodically), which isn't something we see often. That means energy use is the sole factor in our annual cost calculation, which is $25, the lowest of any purifier we tested. The company says the compact machine cleans the air in rooms up to 160 square feet, but it failed to do so in our tests, getting a Poor in both the high-speed and low-speed cleaning tests. It's pretty quiet as air purifiers go, but without the cleaning power, it's not much more than a white-noise machine.
CR’s take: The maker of this tiny air purifier claims it will clean the air in rooms up to 129 square feet. It’s fitted with both a HEPA filter for particle filtration and a carbon filter to remove odors. Our particle reduction tests indicate this model doesn’t cut it. It earns Poor ratings for dust and smoke removal both on high speed and low speed. The filter needs to be replaced every six months, making the annual cost (including energy) nearly $50.
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 scores a Poor in our test for particle removal at low speed and rates a Fair 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 nearly $180 a 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.
For more on air purifiers and how to pick the right model for your home, check our air purifier ratings and buying guide.