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If you’re particularly sensitive to allergens, a higher ACH rating can be useful to constantly keep the air around you clean. If you suffer from allergies or asthma, choose an air purifier with a HEPA filter that can remove 99.97% of most airborne particles that are 0.3 microns or larger. For chemical sensitivity, look for a model that eliminates odors and volatile organic compounds.

The study also looked at the role of what scientists call ultrafine particles, tiny pieces of irritants in the air that people breathe. Raju and his colleagues found there was an association between the presence of these particles in a person’s home environment and a negative impact on lung health. Get reliable, accurate air quality information with these apps and tools.
Winix 5500-2
And on Dark plus Auto, with its primary PECO purification system shut off and its fan on the equivalent of a medium setting, it reduced them by 21.3% and 18.0% . Interestingly, those numbers closely mirror our results on the Auto setting with the PECO system turned on, suggesting the possibility that the Molekule Air mostly relies on its physical prefilter, not its proprietary PECO mechanism, to eliminate particulates. When it comes to handling particulate pollution, the HM400 is a solid performer, reducing particulates to less than 20% of starting levels after 30 minutes on high in our 2017 real-world test (fourth best in our high-setting test) and to 50% on low. But it’s not as fast or efficient as our top pick, the Coway Airmega AP-1512HH Mighty; the dense VOC filter causes this machine to work slower and consume more electricity.

That’s because it is exceptionally difficult to disentangle the known air-quality impacts listed above from other environmental and genetic factors that influence health. Delivering exceptional performance in an attractive form, the Blue Pure 311 Auto suffers only from higher running costs and a lack of a display shutoff. Perfect for bedrooms, playrooms, and living rooms, the AP-1512HH is one of the best performing, most durable, and most economical purifiers we’ve tested. Breathe cleaner air with the UV Air Purifier with AirBRIGHT® Odor Absorption.
ShoppingHEPA air purifiers: An expert shopping guide
However, that’s not always practical, which is why we gave points to lightweight purifiers with handles that made moving them from room to room easy. At a certain point, these results look worse than what you see with no purifier running at all. In a pair of baseline background tests, which we used as a control measure, 0.3-micron particulate levels dropped by 13.9% and 15.3% on their own. That’s due to settling, in which particles fall to a room’s surfaces; agglomeration, in which two or more particles naturally combine to form a single particle; and ambient ventilation, which we standardized for all our tests.

One possible reason the Air performed worse than background reduction is that its fan stirred up the air and kept particles from settling. On Auto, the Air performed worse, reducing 0.3-micron particulates by just 18.0% in ambient conditions and 26.4% in clean conditions. On Silent, it performed worse yet, reducing 0.3-micron particulates by 6.5% and 7.2% .
How Does an Air Purifier Work?
Purifiers rated for spaces larger than the one you plan to use them in can operate on lower, quieter speeds. However, it has excellent clean air delivery rate certifications from the Association of Home Appliance Manufacturers, which in some ways is a more rigorous measurement. (Read more in How we picked.) And it has always delivered exceptional performance in our testing at the 0.3-micron HEPA standard, on both new and old filters.

Yes, HEPA air purifiers are extremely efficient at removing smoke particles from the air. (We use smoke to test them, in fact, so our picks directly reflect their ability to remove it.) But in a wildfire event, purifiers are part of a larger smoke-mitigation strategy. It’s helpful to think of them as a central piece of a comprehensive plan, which we detail in a separate guide to the best wildfire preparedness supplies and strategies. Senior staff writer Tim Heffernan has been at Wirecutter since 2015 and has overseen this guide since then. Since 2017, he has conducted extensive real-world testing of air purifiers in his New York apartment and in Wirecutter’s New York and Los Angeles offices. Tim has also lived with most of our picks, running them 24/7 for months—sometimes years—on end in his apartment.
But we are unlikely to make our own 180-degree turn and recommend it and the Air Pro or Air Mini+. The machines’ high cost and apparently unexceptional airflow relative to similarly powerful and much less expensive HEPA-only purifiers is one reason. Ideal for nurseries, offices, and other spaces where you need quiet, this purifier can remove 99.97% of airborne particles at 23 decibels. It automatically adjusts to real-time conditions to maintain a comfortable air quality, and it has 360-degree air intake to ensure your entire room gets purified. Levoit’s Core 600S is a powerful machine designed for use in spaces up to about 700 square feet at 4 air changes per hour.

Its fan oscillates up to 350 degrees, so it can spread the clear, purified air in nearly all directions. This purifier scored an “Excellent” rating on the highest setting and a “Very Good” rating on the lowest setting in Consumer Reports testing. The purifier also uses the brand’s HEPASilent technology, which Blueair says can filter 99.97 percent of particles down to 0.1 microns. You can also connect to the companion Blueair app to track your air quality. Not only are they smaller and easier to move throughout your house, but they’re also more energy-efficient and affordable than their whole-home counterparts.
CADR measures the “volume of filtered air an air cleaner delivers, with separate scores for tobacco smoke, pollen and dust,” according to AHAM, often measured in cubic feet per minute . The Instant Air Purifier employs a HEPA-13 filter and a carbon filter, as well as an antimicrobial coating on said filters to prevent bacterial growth. Notably, the brand says it can remove 99.7 percent of dust, pollen, smoke, or mold from the air and the purifier has sensors that monitor air quality. How to find the best air purifier for youExperts agree that filtration is key when choosing an air purifier.

It’s slightly more powerful yet also more energy efficient due to a new motor and filter, and it adds an auto setting that adjusts the fan speed to changing air-quality conditions. We have not been able to test it, but we are confident that it will deliver similar, excellent performance. In addition to completing those performance assessments, Tim measured the purifiers’ noise output at a distance of 6 feet, 3 feet from the ground, to determine their highest so-called quiet setting . He also measured their power draw on their lowest, medium, and highest settings, using the medium setting to calculate annual power costs. We do not prioritize smart functionality, which generally means receiving more information from and having more control of an air purifier via an app.
The Alen BreatheSmart FIT50 and T500 are specced for standard usage and as a budget or small-room choice, respectively—but they usually cost at least twice what our picks in those categories do. The GermGuardian CDAP4500 is a small-space unit that usually costs $150 or so—more than our pick in that category, the Levoit Core 300—mostly because it offers Wi-Fi connectivity, which isn’t useful or necessary. Dyson calls the Dyson Pure Cool Me BP01 a “personal purifying fan”—it’s designed to deliver a focused stream of air onto a person’s face from a bedside table or an office desk—and does not consider it a whole-room purifier, so we didn’t test it. These filters also match the Coway replacements in fit and filtration ability, and the package includes a two-year supply of HEPA and VOC filters. The filter on the bottom has been run 24/7 for a year—that’s dust, pollen, and other captured gunk making it dark. We seek the sweet spot of performance and price when choosing purifiers to test.