The best air purifier

By Tim Heffernan, John Holecek

This post was done in partnership with The Sweethome, a buyer’s guide to the best things for your home. Read the full article here.

After spending 180 hours running two laboratory tests of more than a dozen different purifiers by an airborne-particle physicist, we find that the Coway AP-1512HH Mighty is the best air purifier for most people. It outperforms purifiers that cost far more, is the cheapest to own long-term, and maintains its performance for years.

How we tested

The TSI, Inc. 3080/3010 Scanning Mobility Particle Sizer is a specialized particle-test machine we used to count individual airborne particles. Photo: John Holecek

Co-author John Holecek is a former National Oceanographic and Atmospheric Administration scientist and an expert on aerosols—the stuff that’s suspended in the air we breathe. For this and previous versions of our guide, he seeded a well-sealed room in his lab with the smoke from wooden matches and powdered titanium dioxide (it sounds fancy, but it’s just the main component in white paint) to simulate the particulates present in everyday air. He then measured the initial pollution level and the level after 10 and 20 minutes of operation at “normal” settings for each of our air-purifier candidates. (By “normal,” we mean the highest setting that comes in at under 55 dB of noise—at or below “conversational.”) That gave us superfine data on how well the machines’ HEPA (particulate) filters worked under the conditions you’d find in your home and the filter settings you’re most likely to use.

Previously, John also tested air purifiers for their ability to remove volatile organic compounds, or VOCs, from the air. Whereas removing particulate pollution is a physical process that involves trapping particles via inertia in a HEPA filter—a dense mesh of fibers—removing VOCs, which exist as nanoscale molecules, is a chemical process requiring an “adsorbent” (most often activated charcoal) that essentially pulls them out of the air and binds them to the adsorbent. Simply put, we learned that size matters: No adsorbent with a mass below about 2.5 kilograms has much effect on VOCs, and the larger the mass, the better the performance. So for this guide, we nixed this test, and instead used simple mass-of-adsorbent as our standard.

We also looked at noise levels and cost over time (purchase price plus cost of electricity and replacement filters over five years).

Our pick

The Coway Mighty is inexpensive, efficient, and durable. Photo: John Holecek

Within 20 minutes, the Coway AP-1512HH Mighty reduces airborne particulate pollution by 88 percent—among the best and fastest performance we’ve ever seen. It’s one of the most affordable high-performing HEPA-rated air purifiers available, at about $250 upfront and a total of about $577 over five years’ operation (including electricity and replacement filters). And on several absolute measures, it outperforms purifiers that cost two and even three times as much. Finally—and crucially—the Coway Mighty maintained this exceptional performance long-term, even when we measured its performance using two-year-old filters from our 2014 test—filters that had run almost continuously for a year beyond their stated lifespan. We tested the black version; it’s also available in all-white, which may match your decor better.

Runner-up

The elegantly monolithic Winix 5500-2. Photo: John Holecek

If the Coway is unavailable, the Winix 5500-2 is a close runner-up. It, too, is HEPA-certified and rated to clear an area of 350 square feet. After 20 minutes of testing, it slightly outperformed the Coway, reducing particulate levels to 10 percent of their initial levels (versus 12 percent for the Coway). We side with the Coway for its proven long-term performance, its superior long-term cost, and aesthetics. The Winix costs about the same as the Coway upfront, but it is also a bit less energy-efficient and uses slightly more-expensive filters. This means it will end up costing about $130 more over five years’ operation. Because it’s a new model, we don’t have long-term performance data. But if the Mighty is unavailable and you need an air purifier ASAP, it’s a fine choice.

For large spaces and extreme cases

The Coway Airmega 300 looks sleek and is built to clear large spaces. Photo: John Holecek

Though most people don’t need cleaner air beyond what the Coway and Winix offer, those who live with especially dirty air (near a highway, for example) or who are sensitive to chemicals may need more than the Coway and Winix deliver.

If you have severe allergies or other serious health issues related to airborne particles, or if you need to purify the air in a seriously large space, we recommend the Airmega 300. This is a large but attractive machine; it’s HEPA-rated and can clear spaces of about 500 square feet at five complete air-changes per hour (about 1.5 times the coverage of the Coway and Winix), or 1,250 square feet at two complete air-changes. Its unique twin filters permit very high airflow, allowing it to run on lower settings when the air is relatively clean (quieter, less energy) or to rapidly filter very large volumes of air on the highest setting, as you might when allergens or pollution are elevated. In our test, it gave the overall second-best air-purification performance—more a function of its higher airflow and dual filters than inherently superior filtration. It is expensive upfront and costs about $1,400 (including the purchase price) to maintain over five years; this is in line with most of the high-end models we tested, but more than the cost of a pair of Coway Mightys.

For odors and chemical sensitivity

The Austin Air HealthMate Standard HM-400 has a large activated-carbon filter that removes most VOCs and odors.

In our tests for odor/molecular-pollution removal, the Austin Air HealthMate Standard HM-400’s 15-pound activated-carbon filter bested all other air purifiers by a wide margin. (Most air purifiers, including the other picks above, contain no or only token carbon filters, and do effectively nothing to remove molecular pollutants). Its exceptional performance in this area is a big part of why FEMA and the Red Cross chose Austin Air units for deployment at Ground Zero and the surrounding areas in the aftermath of 9/11.

Its annual operating cost ($283, according to calculations at the time of writing) also makes it by far the cheapest high-end purifier to run, but note that this is due to a filter that’s designed to be replaced every five years instead of annually. Against that, its power consumption is rather high, due to its high airflow and the airflow-resistance of the carbon filter; and though it’s HEPA-rated, when running the fan at comfortable sound levels, the Austin Air was less efficient than other models at removing particles from the air. But a little extra background noise isn’t too much to bear if serious health concerns over molecular pollutants are an issue.

This guide may have been updated by The Sweethome. To see the current recommendation, please go here.