Executive Editor, TechHiveMar 11, 2022 3:00 am PST
Image: Michael Brown / IDG
At a glance
Three-way filtration for rooms up to 930 square feet
Easy to use and maintain, with or without the smartphone app
Filter replacement prompts based on volume of air treated, not just a calendar
Filter-replacement timer must be reset with button presses, not in the app
Unattractive industrial design
The Airmega 250S is quiet and very effective at purifying the air spaces up to 930 square feet. If you can give up Wi-Fi connectivity and voice control, the Airmega 250 is every bit as good and costs $50 less.
Price comparison from over 24,000 stores worldwide
Anyone looking for an air purifier for a larger space should give Coway’s Airmega 250S careful consideration. This unobtrusive, box-fan-shaped appliance can monitor and treat the air in spaces up to 930 square feet, with a CADR (Clean Air Delivery Rate) of 230 for pollen, 249 for smoke, and 261 for dust.
The Airmega 250S can connect to your Wi-Fi network, which adds some appealing features that I’ll discuss in the Wi-Fi section, below. If you can live without that connectivity, everything else in this review also applies to the Airmega 250 (which I’ve also tested). That model lacks Wi-Fi, but it costs $50 less (MSRP, that is. Check street prices and you might find the difference to be much smaller.)
This review is part of TechHive’s coverage of the best air purifiers, where you’ll find reviews of the competition’s offerings, plus a buyer’s guide to the features you should consider when shopping for this type of product.
The Airmega 250S draws air through its 17 x 14-inch (HxW) front grille, where a micromesh prefilter captures larger particles, such as hair, pet fur, and dust. The disposable Max2 filter behind the prefilter consists of an activated carbon filter to remove odors and VOCs (volatile organic compounds) glued to a HEPA filter. Coway says this combination will trap 99.99 percent of the remaining airborne particles down to 0.01 microns in size, including viruses and bacteria. Clean air is vented out the top of the unit. This design allows you to place the 19.7 x 18.5 x 8.3-inch (HxWxD) purifier up against a wall, where it’s out of the way.
Michael Brown / IDG
The prefilter is easy to remove for periodic cleaning with a vacuum or by rinsing it under a faucet. Simply pull the two tabs on either side of the front panel toward you and then lift the prefilter’s handle. The prefilter needs to be cleaned every three weeks.
Coway estimates that the Max2 filter should last for a full year; replacement filters cost $79. To replace the Max2 filter, you just pull the front grill past the stop needed to replace the prefilter, lift the prefilter out, and then pull the tab on the Max2 filter behind it. An LED on top of the cabinet lights up when it’s time to clean the prefilter, while a second LED glows when it’s time to replace the Max2 filter.
To the right of the filter LEDs, a 3.5-inch color LED bar informs you of the current indoor air quality, glowing blue for good, green for moderate, yellow for unhealthy, and red for very unhealthy.
Using the Airmega 250S
Apart from filter maintenance, the Airmega 250S can operate pretty much autonomously and very quietly. I could barely tell the unit was operating most of the time; in fact, I needed to stand right next to it to hear the soft whir of moving air. I deployed the Airmega 250S in the dining area of my small home and would hear a moderately loud whoosh while frying bacon and similar foods in the adjacent kitchen, but the noise wasn’t loud enough to disrupt conversation or to blot out the sound of the TV in the living room. I often forgot the appliance was even there.
Indeed, I found little reason to operate the Airmega 250S in anything other than “Smart Mode: Auto” (I’ll discuss its three other modes in a bit). The Airmega 250S will monitor your air’s quality in real time and automatically adjust its three-speed fan accordingly. When the room in which the purifier is operating is dark, and measured air quality is good (level 1) for three minutes, the purifier will automatically go into a low-power “Smart Mode: Sleep” state. If ambient light is detected for five minutes, or air quality deteriorates to moderate (level 2) or worse, the purifier will return to operating in “Smart Mode: Auto.”
Michael Brown / IDG
In “Smart Mode: Eco,” the air purifier will turn off its fan to conserve energy if the measured air quality remains good (level 1) for more than 10 minutes. Here again, if air quality deteriorates, the purifier will restart its fan and operate it until air quality improves and remains at level 1 for more than 10 minutes. A button on the top right-hand side of the Airmega 250S lets you switch between the Auto and Sleep modes I’ve already described as well as a “Rapid” mode that will operate its fan at high speed (the same as if air quality is determined to be level 3 or very unhealthy). When air quality returns to level 1 for more than 5 minutes, or the purifier operates for more than 60 minutes, it will automatically switch back to Auto mode.
If you’d prefer to exercise more control over the device, another top-mounted touch-sensitive button lets you choose between 250S’s three fan speeds, and another lets you set a timer that will automatically turn it completely off after one, four, or eight hours. A child lock feature disables all the Airmega’s buttons if you have curious rug rats in the house.
Connect the Airmega 250S to your Wi-Fi network (2.4GHz networks only) and you can control the purifier with Coway’s IOCare mobile app (available for Android and iOS). With network connectivity, you can also control the air purifier in-app buttons that replicate the unit’s physical buttons. You can use voice commands spoken to Amazon Echo and Google Home smart speakers and displays, too. So, instead of pulling out your smartphone or tablet to switch operating modes, fan speeds, or set up a sleep timer, you can tell Alexa or Google Assistant to do it. The appliance is not compatible with Apple’s HomeKit ecosystem.
The IOCare app also offers some other benefits you won’t get with the non-connected Airmega 250 model. The app will display your current indoor air quality, based airborne 2.5- and 10-micron particulate matter, as well as charts reporting the average and maximum levels of that matter for the last 24 hours, 7 days, and 30 days. And instead of watching for the indicator lights to change when it’s time to replace the purifier’s prefilter and Max2 filter, the app will send you a push notification when the time comes.
Michael Brown / IDG
You can also see a visual presentation of each filter’s remaining useful life presented as a bar chart and a percentage. And rather than simply counting down the days that elapse between filter changes, the appliance tracks the volume of air it has processed and prompts filter changes based on that data. One thing I did find annoying, however, is that the app doesn’t provide any means of resetting the filter life monitor. This must be done by pressing a sequence of buttons on the device itself. Pro tip: Don’t misplace Coway’s excellent and detailed user manual, because that’s the only place you’ll find the instructions for this Morse code-like step.
The Airmega 250S and Airmega 250 are good values
Being a smart home enthusiast, I would have no problem paying an extra $50 to get Wi-Fi connectivity and Coway’s IOAir app. Pretty much everything in my previous smart home was controlled by voice commands—including the window shades and blinds—and I’m in the process of converting my very old (but new to me) residence into a modern smart home. If you’re not as nerdy as I am, you might not see the value in that connectivity, in which case I’d recommend the Airmega 250. The two appliances are identical apart from Wi-Fi, and they’re both excellent air purifiers for larger spaces. If you need coverage for even larger spaces, take a look at the NuWave OxyPure Smart Air Purifier, which is rated for up to 1,200 square feet.
Michael is TechHive's lead editor, with 30+ years of experience covering the tech industry, focusing on the smart home, home audio, and home theater. He built his own smart home in 2007 and used it as a real-world test lab for product reviews. Following a relocation to the Pacific Northwest, he is now converting his new home, an 1890 Victorian bungalow, into a modern smart home.