I cannot overstate the importance of having an air purifier that not only has enough power to actually purify a room's air but also caters to your home's particular needs. Pollutants like wildfire smoke, pollen, unventilated gas stoves, pet allergens, and even litter box odors can be potentially harmful additions to the air you breathe in your home.
Air purifiers from Coway have been a consistent top pick in our guide to the Best Air Purifiers for years, including the Coway Airmega Mighty2, which was released in March this year. Its predecessor, the Coway Airmega Mighty, had been our reigning “Best Affordable Air Purifier” for many years as well. I was excited to test the newest mid-size option built for medium to large rooms in Coway's Airmega line, where it sits between the compact Airmega 50 or 100 and the higher-capacity 350 or 450 models.
Released at the end of August, Coway’s Airmega Halo is an affordable, lightweight air purifier that aims to deliver whole-room air purification at an accessible price point. Plus, its focus is on promoting a healthier night's sleep with smart sleep features and quiet noise levels when in sleep mode.
Overall, it delivers on most of its promises, but I ran into some problems during field-testing that made me question its sensor, and I wish it had more transparency with pollutant levels.
The Halo is only 9. 7 pounds, making it lightweight and portable as far as air purifiers go, but it doesn't have accessibility features like a top handle or wheels for easier moving. It has a small cutout in the back to grip, but because I have an upper-limb disability, moving it was awkward—I essentially had to hug the purifier to maneuver it, since I don't have large hands that can easily grip the inlet.
The purifier's cylindrical design with a 360-degree air-intake structure draws in polluted air from all sides, making for fewer spatial constraints and more options for placement around the home. The inside of the machine uses Coway's HyperVortex filtration system, which is an aerodynamic fan and duct design that Coway states is “inspired by eagle wings and golf ball dimples.” It uses wing blades to stabilize airflow, along with aerodynamic blades for powerful airflow for the generator fan and dimples to reduce air resistance for smoother air intake.
Setup was extremely easy—I just needed to unscrew the bottom, remove the filter from the plastic protective covering, screw the bottom back on, and plug it in. There's no need for a Wi-Fi connection, no app, and no remote. I started testing air purifiers earlier this year, and I've found I actually like having a connected remote, or better yet, an app that allows me to monitor air quality and adjust settings from afar. This model had neither. I also appreciate getting transparent numbers of pollutant levels directly from the machine rather than relying on colored lights, but this machine had the latter.
Inside, the Halo has a cylindrical IEST-certified HEPA three-stage filter that claims to capture 99. 97 percent of nano-sized particles down to 0. 3 microns, but in my opinion the coolest feature is the MegaScan Particle Sensor, which continuously monitors the air in real time to detect smoke, fine dust, and allergens down to PM2. 5. PM2. 5, typically used as the standard measurement for air purifiers’ ability to measure and lower levels of microscopic allergens or pollutants, are tiny airborne particles that measure 2. 5 micrometers or less in diameter. They are particularly dangerous because their size means they can penetrate deep into the lungs and cause serious illness like asthma, heart disease, and lung cancer.
From the purifier's top touchscreen panel, you can control fan speed, timer, and settings. On the quietest sleep setting, my decibel monitor app wasn't even able to pick up the noise, as the fan wasn't perceptible above the ambient noise of my house, even when I switched off all nearby appliances. Coway claims it's 17 decibels in sleep mode, which I believe after not even being able to hear the machine in this mode. On the highest turbo setting, my decibel reader had it hovering around 75 decibels, which is akin to running a dishwasher or a vacuum.
As part of the Airmega Halo's sleep features (in addition to whisper-quiet functioning), it has a low yellowish night light when in sleep mode, but this can also be turned off so the top panel is completely dark. It has a light sensor and automatically enters sleep mode, dimming lights and noise level when low light is detected.
When in smart mode and it's dark for more than three minutes, the machine will automatically enter sleep mode. If the pollutant levels are “good” for more than three minutes, the fan stops automatically to save energy. But if it detects pollutants, it will restart the fan.
It has four lights indicating air quality levels: blue for good, green for moderate, yellow for unhealthy, and red for very unhealthy. The colored lights show in a halo around the top of the machine. I found it sort of tough to distinguish between levels at a glance because this color-coding system differs from the US AQI standards of green for good, yellow for moderate, red for unhealthy, purple for very unhealthy, and maroon for hazardous.
Hopefully, you come to WIRED Reviews because we actually vigorously test the gear we recommend. I didn't just read the specs online and flip through the instruction manual—this machine was put through some intensely bad air to see if it could hold its own.
As with all air purifiers I test, the Halo was put through testing in various unhealthy air quality situations. I used this model for nearly a month, moving around my house to test in different locations: when cooking on my unventilated gas stove, under my living room window that draws in a lot of building and exhaust fumes, and outside my cat's litter box. Additionally, I use an indoor air quality monitor to test pollutant levels against what the machine claims.
I also measured the Airmega Halo's efficacy by using a sealed tent and smoke pellets to see how quickly each air purifier clears the pellet smoke and returns the air to healthy quality when on auto mode. I run this hands-on field test for every air purifier I test. I measure first visually, using a timer to measure how long it takes to engage and clear the smoke by eye. Then I time how long it takes for the air quality to return to Healthy, using my air quality monitor. I also usually like to measure it against the pollutant's numbers on the connected app or display on the air purifier machine—since the Halo doesn't have either, I measured against the colored lights that indicated pollutant levels.
Now, here's where I started encountering problems. In the smoky sealed tent, the machine was in auto mode, and it took one minute and 21 seconds for the smoke to visually clear. It also should be noted that the Halo did kick into its highest speed, but never engaged in actual turbo mode when confronted with the smoke, which leads me to believe that the turbo mode can only be manually turned on.
The machine seemed to be doing its job fairly well—the smoke never clouded the tent so badly that I couldn't see the machine through the fog. And surprisingly, the indicator lights never even flashed red or yellow for very unhealthy levels, only flashing green for moderate pollution. This struck me as odd; no matter how good this air purifier is, it should be able to detect that a literal smoke bomb is delivering unhealthy levels of pollutants. After one minute and 45 seconds, the smoke had cleared, and the air purifier was glowing blue—all's good and healthy here, right? Wrong.
Since the machine unfortunately doesn't have a built-in PM2. 5 or other pollutant sensor display to measure levels, only the indicator lights, I went into the tent to measure the pollutants with my personal air quality monitor. When I unzipped the tent, my eyes immediately started tearing up from the pollutants, and I needed to get out because I couldn't breathe. I'd hardly call that healthy. My monitor showed a PM2. 5 level of 46. 5 micrograms per cubic meter, which translates to an AQI equivalent of 128 —"unhealthy for sensitive groups" on the US AQI scale (which is orange-colored for US AQI standards).
I was also shocked to see the machine had set itself back to 1, the lowest setting in smart mode, despite the air smelling bad and my monitor's hazardous reading. Almost six minutes later, my personal monitor showed it was back to normal levels again—an alarming, almost-four-minute delay. In field tests I do on all air purifiers, these numbers have always been similar. This was the first time there was such a large discrepancy between my air quality monitor and the air purifier's internal system.
I manually turned it to turbo mode afterward, hoping to clear out the air even more and reduce the odor. I even moved the machine into my bedroom with another air purifier running on its highest setting, but the smoke pellet smell lingered the entire night.
The machine itself now smelled bad, so I tried to remove the filter and vacuum any lingering pollutants from the filter's meshy material. I tried unscrewing the bottom, and it wouldn't unscrew. Uh-oh. I think I had put it on wrong or twisted it too tightly. I don't believe this would've affected the test results above, as none of the air vents or panels are on the bottom and, when I checked internally, the air filter was in the correct position. With my weaker grip strength due to my disability, it wasn't easy to remove the bottom panel to access the filter.
I asked a few air quality experts about the discrepancies between what I measured and the machine's internal reading. Most agreed that reputable companies like Coway put their air purifiers through extensive lab testing and trust that the internal air purifier system is working effectively.
One possible reason folks kept pointing to is that the discrepancies are probably due to the different placements of the sensors. “The stand-alone monitor [is] nearer to the source of the pollution, whereas the sensor built into the purifier is inside the unit and may be measuring air that has already gone through the device," said Joe Haycock, vice president at Fresh Air Concepts, a company specializing in residential and commercial HVAC systems. “They also might use different sensors or different criteria as to what constitutes a healthy level.”
Overall, this machine is well priced for its power, with an ability to completely purify a 1,898-square-foot room in an hour. (Though this is slightly misleading—for an ideal four to five air changes per hour, the ideal room size would be closer to 474 square feet.) Plus, if you're looking for a purifier for a baby's room or are an especially light sleeper, the Coway Airmega Halo with enhanced sleep features would be ideal. In real, day-to-day life, you won't be putting the machine through the rigorous tests like I did. Still, my results—and the lack of a numerical display—make me question whether the purifier is working as effectively as its colored lights suggest.
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