Most of us spend a lot of our lives indoors — reports say that people in the US, the UK and Canada are inside about 90 percent of the time. Those same reports also note indoor air can be far more polluted than outdoor air, thanks to things like cooking emissions, building materials, cleaning supplies and pet dander. One way to clear the air is to increase ventilation, which can be as simple as opening up windows. But if the air outside is also unhealthy — such as from wildfires, smog or a high pollen count — letting in the outdoor air might not be an option. That’s when air purifiers get to work. We tested a handful out of the hundreds of options out there and found the best air purifier for most people, along with a few alternatives: one with a higher design aesthetic and one for a smaller space. We also break down how air purifiers work and point out what these machines can and can’t do.
What an air purifier can and can’t do
There are three key pollutants that adversely affect the quality of the air you breathe: volatile organic compounds (VOC), particulate matter (PM2.5 and PM10) and carbon dioxide. VOCs are emitted gasses that can come from cleaners, off-gassing plastics, paint, solvents, fragrances, cooking food and, ironically, air fresheners. VOCs are most closely related to odors you can smell. High levels can irritate your breathing passages, cause headaches and may become cancer-causing over time. Air purifiers with activated charcoal components can help clean VOCs from the air.
Particulate matter is usually discussed as PM2.5 and PM10, with the numbers indicating particle size in microns. This is dust, dirt, mold, smoke and, again, emissions from cooking food. Higher levels of PM can lead to respiratory irritation, allergy symptoms, respiratory infections and potentially lung cancer. Air purifiers that include a HEPA or particle filter can help remove airborne particles from your space.
Carbon dioxide is what humans and pets breathe out. Elevated levels can cause dizziness and lethargy. But no air purifier can reduce CO2 levels because the molecules are so small. Plants can help to some extent, but really the only solution is opening a window or otherwise ventilating the space.
There are no federal standards for air purifiers, but the state of California does require all air cleaners sold in the state to be certified by the California Air Resources Board (CARB). All of our top picks here have met that certification.
What to look for in an air purifier
HEPA filters and other filter types
An air purifier isn’t an overly complicated device. Smart modes and app connectivity aside, they’re not much more than a filter and a fan. The latter pulls air through the former to capture particulate matter and other unhealthy elements so you don’t breathe them in. The type of fan can make some difference — it should be powerful enough to pull in air quickly, but also quiet enough on its low speed so it can unobtrusively clean all day long.
Filters, on the other hand, are more varied. Most have two or more layers, typically a pre-filter, an activated carbon component and sometimes a particle or even a HEPA filter. The pre-filter is made from a fine mesh that captures big stuff like pet hair and larger chunks of dust. Sometimes this part is separate from the more technical filters — which means you can remove and clean it without needing to swap out the whole thing. For all-in-one filters, you can vacuum the outside of it to remove larger particles.
An activated carbon or activated charcoal layer is extremely porous, tightly packed coal that presents a vast amount of microscopic surface area to the passing air. Gaseous chemicals, VOCs and other molecules become lodged in the crannys and stick. This is the layer that gets rid of odors.
Most air purifiers include a particle filter. Some of those can be called “true HEPA” (high-efficiency particulate air) filters — meaning they conform to the standards set out by the DOE. Particle filters are made up of pleated masses of ultrafine fibers that force air to take a convoluted path in order to pass through. This traps and absorbs tiny molecules of smoke and dust, allergens like dander and pollen, and some viruses and bacteria.
Since all of these air filters physically trap particulates, they’ll eventually fill up and become less effective. Most manufacturers recommend replacing the filter every six months, while others claim a year-long life span. Most smart air purifiers will let you know in the app when it’s time to replace. When you’re considering a unit’s cost, be sure to factor in the expense of replacement filters, which you may end up buying twice a year.
Room size
Air purifiers list their cleaning capabilities in terms of room size and frequency of air exchanges, sometimes listed as clean air delivery rate (CADR). For example, a smaller one might say it can exchange the air in a 500-square-foot room twice per hour. So that model should be able to pass all of the air in a 250-square-foot room through the filter every 15 minutes, but a 1,000-square-foot room would probably be outside its effective range. Of course, there’s no standard for manufacturers to adhere to when it comes to these calculations, but typically, larger air purifiers can handle large rooms.
Where you put the machine makes a difference, too. Since it requires airflow to effectively clean air, somewhere close to the middle of the room and at least a foot away from furniture, walls and other potential blockages is ideal. That’s not always practical, so aim for getting it as close as you can to the center of your space while maintaining a one-foot clearance all around.
Controls
In our testing, we focused on Wi-Fi-connected “smart” air purifiers with companion apps that can monitor air quality and adjust the fan speed as needed. Within the apps, you can control auto-clean settings, set timers and schedules and check the health of the filter as well. Most will remind you when it’s time to get a replacement, and let you order one directly from the manufacturer through the app. You can also see the current and historical readings from the internal air quality (AQ) sensor. Most determine air quality through an optical particle meter, though some brands like Dyson and Molekule also include chemical sensors for VOC measurements. When levels of particulates become elevated, the fans switch up to high speed to move more air through until the quality improves.
Most smart purifiers also work with voice assistants, so if asking Alexa to turn on your air purifier makes your life easier in some way, you can do so. If you don’t want to talk to an AI or grab your phone to control your purifier, getting a unit with simple on-board controls is a good idea. These can be as basic as buttons with indicator lights or as elaborate as a touchscreen panel. At minimum, it’s good to have a way to control the fan speed and turn on or off auto mode on the device itself.
Design
As we mentioned, sticking the device as close to the middle of the room is helpful for getting the best performance. That means you’ll be looking at it a lot, so design considerations matter. Most purifiers are cylindrical towers with fan vents up top. Units meant for larger rooms are not small, weighing between 12 and 20 pounds and reaching two feet tall (or in the case of the Dyson Purifier Cool, three and a half feet). Some, like Coway’s Airmega IconS, take on more furniture-like designs to blend in. Others, like Dyson’s, are conspicuously designed to stand out.
When an air purifier just isn’t enough
The most striking bit of knowledge I picked up from testing air purifiers is how effective opening windows can be on indoor air quality. What took an air purifier a half hour to clear out took mere minutes when I opened my front door and a few windows. Every variable measured by the air quality sensors, including VOCs, PM, and particularly CO2 levels (which air purifiers can’t alleviate), improved dramatically after exposure to fresh air — significantly faster and better than any machine we tested. Even on very cold or very hot days, it might be worth it, even if your doors and windows are only open for a few minutes. True, my HVAC system had to work a little overtime afterwards, but venting a room was the most surefire way of getting air quality quickly back in the green. Of course, if the air outside is unhealthy from wildfire smoke or run-of-the-mill pollution, or if you’re dealing with seasonal allergies, throwing open the windows won’t work and an air purifier might be the best way to consistently clean things up.
How we test air purifiers
My living room is not a science lab; there’s far too much pet hair for that to be the case. Still, I went beyond just turning stuff on and sniffing the air by acquiring two consumer-grade indoor air quality monitors that performed well in laboratory assessments, the Element from Element from Awair and the uHoo Smart Air Monitor. I conducted burn tests by measuring the ambient air quality, then burned a brick of piñon incense for twenty minutes and measured the air again. Then I ran one purifier at its highest speed for thirty minutes and recorded levels, then ran the unit on the lowest setting for a half hour and remeasured. I made note of the sound levels using a simple iPhone app to compare one machine’s noise level to the next.
Over the course of a month, I used each unit in different scenarios (such as in the basements where the cat litter boxes are) and tried out each device’s smart features, controls and auto modes. I also just lived with them and evaluated how they fit into everyday life. As new purifiers come on the market and as we become aware of other units that seem worthy of inclusion, we’ll continue to test them and update this guide accordingly.
Photo by Amy Skorheim / Engadget
Filters: Pre, activated carbon, particle | Auto Mode: Yes | App-connected: Yes | Sleep Mode: Yes | Coverage area in 30 minutes: 1,000 sq.ft. | Max decibels: 64 | Weight: 14 lbs | Filter replacements: $50
The Levoit Core 400S Smart Air Purifier isn’t trying to be anything fancy. It’s a simple white cylinder with holes for air intake and a black ring of vents on top. Simple touch controls in the center of the vents are easy to suss out, letting you adjust the fan speed, enable auto mode and turn on a sleep setting, which drops the fan to the lowest intensity and shuts off the display lights. The internal sensor measures particulate matter at 2.5 microns, which displays in the center of a lighted ring near the controls. The ring turns blue when all is well and moves through to green, orange and red as air quality levels deteriorate. In auto mode, when it detects a drop in air quality, the fan increases speed until levels go back down.
Even at its highest level, the fan isn’t terribly loud, peaking at around 62 in the Decibel Meter app and leaving my cat undisturbed on the couch nearby. Yet the force of the air coming out is strong and feels on par with output from purifiers that are quite noisy (which made the cat run away).
The Core 400S claims a half-hour air exchange rate for a 1,000-square-foot room and combines the three main filter types — pre-filter, activated carbon and particle — into a single ring. Perhaps the best part is a replacement filter is only $50, half the price of some competing brands. In multiple burn tests, the Core 400S reliably got the room back to its starting level in about a half hour of running on high. Auto mode does a good job of reacting to drops in quality, kicking on to a higher fan level nearly every time someone in the house cooks and after an incense burn.
This air purifier connects to the VeSync app; setup is easy, but the app itself is overpacked. There’s a forum, a wellness tab and a shopping page where you can buy not just Levoit products, but also devices from sister brands Etekcity and others. But as far as controlling the Core 400S itself, the in-app controls are easy to use and nicely laid out.
- Easy on-board controls
- Reliably improved the air quality in our tests
- Inexpensive replacement filters
- High speed is powerful, but not overly loud
- The companion app is over-stuffed
- Ho-hum design
Photo by Amy Skorheim / Engadget
Filters: Pre, activated carbon, particle | Auto Mode: Yes | App-connected: Yes | Sleep mode: Yes | Coverage area in 30 minutes: 547 sq.ft. | Max decibels: 58 | Weight: 6 lbs | https://www.standards.doe.gov/standards-documents/3000/3020-astd-2015: $36-40
The best pick for a tiny room turned out to be the mini version of our overall pick: the Levoit Core 300S. Manufacturers recommend elevating smaller air purifiers on a table or stool — where you’re even more likely to notice them. From a looks perspective, I prefer Molekule’s Air Mini+ better, but Levoit’s model goes for nearly $200 less and replacement filters are a third of the price. The Air Mini+ did perform slightly better than the 300S in my burn test, but the results were very close — and when you’re dealing with measurements in the parts-per-million, a difference of a hundred or so in the numbers is near negligible.
Simple controls at the top of the Core 300S turn on auto mode, adjust fan speed and more. You don’t get the PM meter readout that the larger unit has on this model, but you still have the lighted ring that shines blue when the air is clear and goes to red when things get unhealthy. Of course, you can always head to the app to see the PM2.5 measurement, as well as to do things like set schedules and timers and enable different auto modes. You can turn on a quiet auto mode, which will raise the fan speed when air quality goes down, but won’t ever use the highest fan speed. There’s also an efficient mode that lets you set the size of the room and it will blast the highest fan speed for the amount of time it takes to do one air exchange, before dropping back down to low — sort of like an on-demand reset for the room.
The lowest setting is remarkably quiet. Unless the room is fully silent, I have to hold my hand over the vents to make sure it’s on. The highest speed isn’t terribly loud at around 58 decibels, yet the air comes out forcefully.
- Simple on-device controls
- Low mode is very quiet
- Inexpensive replacement filters
- Fairly uninspired white plastic cylinder design
Photo by Amy Skorheim / Engadget
Filters: Pre, activated carbon, HEPA | Auto Mode: Yes | App-connected: Yes | Sleep mode: Yes | Coverage area in 30 minutes: 640 sq.ft. | Max decibels: 60 | Weight: 19 lbs | Filter replacements: $89
After putting effort into your living space’s design, you might not be thrilled to stick a giant plastic tower in the middle of the room. Coway’s Airmega Icon S came out in mid-2022 and looks more like a tiny mid-century-modern credenza or speaker cabinet than an air purifier. Coway came out with the comes in a neutral beige tone and even has a little shelf up top that doubles as a wireless phone charger (because of course it does). Lighted controls appear with a tap — and disappear when you’re done using them — letting you control the fan, timers, auto mode and lights. There’s a PM2.5 readout and an LED light that glows from under the shelf and turns from blue to green, yellow and orange as air quality devolves. The LED light is bright, but you can turn both it and the PM readout off.
The Icon S measures particulate matter to control its auto mode and reliably turns up the fan after I make dinner. The fan has just three speeds, which honestly seems like enough. At full blast, it’s still a reasonable volume, yet powerful enough I can feel air movement ten feet away.
The app wouldn’t connect at first, which was frustrating, and even after getting it to work, I found it to be laggy and not very compelling. It has the same basic controls as the unit itself, plus a historical report on air quality levels and the overall health of the filters. But I really only used any of the apps for the purpose of evaluating them; the rest of the time I just used the touch controls atop the unit.
The major drawback is the price. At $699, the Airmega Icon S is expensive — but it does have one advantage many other models lack: a removable and washable pre-filter. As mentioned above, the pre-filter captures the big particles like pet hair and big dust chunks. Since most filters are a single unit, the best you can do is vacuum the outside, sucking up the debris to give it a refresh. Here, you can remove the entire thing, give it a wash, dry it out and stick it back into the machine. The app will even tell you the health of the two filters separately so you know when it’s time to give it a clean. Replacement filters for the combined true HEPA and activated carbon layers costs $89.
- Attractive and subtle design blends in
- Removable pre-filter is easy to clean
Other air purifiers we tested
Sensibo Pure
At $229, and nearly always on sale for $130, I had the Sensibo Pure pegged as a contender for a budget pick. Unfortunately, replacement filters are $99 unless you subscribe to automatic shipments and many of the app features are behind a paywall as well. It’s not certified by CARB and underperformed many of the other units in the burn test, though it did return the air back to a “good” rating according to the air monitors after 30 minutes. The design is inoffensive, it’s not overly loud and it does integrate with Sensibo’s smart AC devices, so if you’re already happy with one of those, this may be a decent option.
Dyson Purifier Cool
Like all Dyson products, this air purifier is dripping with design. It looks like no other unit on the market and it’s up to you to decide whether you like that or not. I was indifferent to the looks, but appreciated the slick and informative app, which not only displays indoor air quality, it also shows what conditions are like outside, using a clever house graphic to differentiate the two sets of numbers. I also like that it detects VOCs as well as particulates and the auto mode seemed to read the room accurately. The air coming out of the fan did indeed feel cool, though at first had a strong plastic odor. Unfortunately, it was the lowest performing unit during two separate burn tests and had repeated connectivity issues.
Molekule Air Pro
The Molekule Air Pro comes from a brand that pays keen attention to aesthetics. It and the app have that Instagrammable, muted-modern look that countless clothing and bedsheet brands emulate these days. That style doesn’t come cheap as the Air Pro costs over $1,000 and requires $140 filters. The company came under fire for and had to stop making many of its claims about its filtration system, which may have led to it filing for bankruptcy last year. Molekule is still able to tout its patented photoelectrochemical oxidation, which the company says destroys pollutants at a “molecular level.” In my tests, it performed almost as well as the others in improving VOC and PM2.5 levels. But it’s also very loud: When auto mode kicked the fan into high gear, it would make me tense. Also, I found the unit often indicated “bad” or “very bad” levels when my two monitors indicated the air quality was actually pretty good.
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