here are the key facts: within 20 minutes, our pick 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.
And on several absolute measures, it outperforms purifiers that cost two and even three times as much. finally and crucially, the coway mighty maintains this exceptional performance long-term, even when we measured its performance using two-year-old filters from our 2014 test—filters that had been run almost continuously for a year beyond their stated lifespan.
if the coway is unavailable, the winix 5500-2 is a close runner-up. it, too, is hepa-certified and rated to a very large 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 proven long-term performance and 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. and subjectively, it’s also less attractive than the mighty. but if the mighty is unavailable and you need an air purifier asap, it’s a fine choice. (note: the 5500-2 replaces our previous runner-up, the nearly identical winix plasmawave 6300. the 6300 will phased out within a year, but replacement filters will remain available, so if you bought one, there’s no need to upgrade.)
while 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. here are our picks for these extreme cases.
if you have severe allergies or other serious health issues related to airborne particles, we have a new step-up pick: the coway airmega 300. this is a large but attractive machine; it’s hepa-rated and designed to 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. in our test, it gave the third-best absolute performance, 87 percent reduction (not statistically different from the mighty’s 88 percent) in particulate levels over 20 minutes versus the original measurement.
That said, it’s designed more for long-term, large-space, and/or high-intensity use. 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 or if you need to clear a large space—say, an artist’s studio or loft.
it is expensive according to our calculations 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 it’s more than the cost of a pair of coway mightys.
if you live in a problematic environment with high levels of both particulate and molecular pollutants (e.g., near a farm where bioicides are sprayed, a chemical/power plant, or a refinery) or are particularly sensitive to odors or other volatile organic compounds common in homes (like formaldehyde), we recommend the austin air healthmate standard hm-400.
in our tests for odor/molecular removal, its 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—their strength is on larger-particulate pollutants like dust). 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. also, the austin air was less efficient than all other models at removing particles from the air when running the fan at comfortable sound levels, even though it’s hepa-rated. but a little extra background noise isn’t too much to ask if serious health concerns over pollutants are an issue.