Review: Airmega 400S Offers Smart, Silent Air Purification

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This home air purifier features HEPA filters and a real-time air quality sensor, and can filter the air completely twice per hour in 1,560 square feet of living space.

Indoor air pollution may be one of the modern world's invisible menaces, and the air inside our homes can be more polluted than the air outdoors, which is quite disconcerting considering that we most likely believe our homes to be the safest place for us. Knowing what types of air pollution sources we may be bringing into our homes, and then choosing less toxic alternatives, is one approach to a healthier home, but a second solution is to employ an air purification system as well, in order to filter out as much of these potentially harmful allergens, dust, toxins, and volatile organic compounds (VOCs) as possible.

There are quite a few air filtration and purification devices on the market right now, some of which claim to 'destroy' indoor air pollutants by breaking them down into harmless elements, and others which rely on HEPA filtration systems that can trap and remove particulates as small as 0.3 microns from the air. I recently spent several months trying out one of these types of air purifiers, the Airmega 400S, and although my findings were purely anecdotal, I believe that it makes a great addition to a home's environmental defense system.

The Airmega comes in two basic models, the 400 and the 300, with both models available in the 'S' configuration (WiFi- and app-enabled "smart" features) that allows users to check air quality, check filter life, set up a schedule, and manually adjust the settings of the air purifier. The 400 covers 1,560 square feet (145 square meters) of space and delivers two complete changes of air per hour, while the 300 is rated for two air changes per hour for 1,256 square feet (117 square meters), or half that size of an area if 4 air changes per hour are necessary. The 400 model is a tall cube measuring about 23 inches high by 15 inches square, and weighs about 25 pounds, with handles on two sides, so it's not very hard to move around.

The Airmega has dual air inlets and dual filters for each of those, with a washable pre-filter (a fine screen) first trapping larger particles before they enter the filter chamber, where the Max2 filter set (comprised of a combined activated carbon and "Green True HEPA" filter) removes the balance of the air pollutants. According to Airmega, the filter "reduces more than 99% of volatile organic compounds (VOCs) from the air, as well as fumes such as NH3 and CH3CHO," and "reduces up to 99.97% of particles in the air." The unit needs to be situated in a location that has open areas on either side to allow for a good flow of air to the filters, and because the a filtered air is blown out of the top of the unit, it shouldn't be placed under a table or cabinet that might impede the air flow.

Several modes of operation are possible right out of the box, either in Smart mode, which uses the unit's onboard sensor to monitor the air quality and adjust the fan speed accordingly, or manually by selecting one of three fan speeds. In Smart mode, when the sensor registers good air quality for the past 10 minutes, it will turn off the fan until needed again, and in Sleep mode, will do the same when the room is dark and air quality is clean for 3 minutes, as well as turning off all indicator lights. Additionally, a custom schedule can be set for operation of the Airmega, and because it's WiFi-connected, the unit can be operated remotely through the accompanying app, or through Amazon Alexa.

As far as my personal experience with the 400S, it was really easy to set up on my local network and connect to it with the app. The Airmega unit was very quiet while in operation - whisper-quiet, in fact, on the lowest fan speed - and although its design has a much more modern look to it than any other appliance in my home, the only design feature that I took issue with is the fact that the fan blows out of the top of the unit. Because of that, nothing can be placed on top of it, which is pretty difficult to avoid in a family with three young kids at home. However, the cord is long enough for it to be placed in a convenient location (your mileage may vary), and the cord features a woven covering in matching colors, which makes for a more aesthetic option than your standard black plastic appliance cords.

Although I used the app with the Airmega at first, to set it up and get to know it a bit, I ended up mostly using it in Smart mode, which meant that I didn't have to do anything other than check the pre-filters once in a while. One of the touted features of the Airmega, the visual display of the current air quality on the front of the unit, I really didn't care for, and although you can turn it off manually, I wish there was a way to turn it off completely, as I have no desire for more appliance lights in my home. Another feature that kind of bugged me is the audio chimes that sound when it powers on and when it connects to the Wi-Fi network. If you leave in plugged in and connected, it's no big deal, but I moved it to different rooms on occasion, and then needed to use the outlet for something else fairly regularly, and even though the chimes aren't very loud, the fact that they would sound every time and couldn't be turned off was a weird feature to me.

I didn't do any testing of the air quality in my home either before or during the use of the Airmega, so all I have to rely on is my own senses, but there is a discernible difference in the air that comes out of the top of the unit, and based on the amount of material that collects on the pre-filter alone, it's removing a significant amount of stuff from the air. I live in a very dusty area, and we often have the windows and door open, as well as having two dogs that contribute their own brand of particles to the home, so having cleanable pre-filters is a big plus. Removing the prefilters is simple to do, and although the company recommends vacuuming them, I just rinsed and dried them, which was quick and easy. I haven't had to change the filters yet, as they are not cleanable and must be replaced, but the estimated life of the filters is about 12 months (again, your mileage may vary). Although you don't have to use the app to know when to wash the pre-filters or change the filter, because visual indicators on the top of the unit display that information, it wasn't obvious at all how to reset the unit once the pre-filters were washed, in which case the app Help feature came in handy.

Overall, I like the Airmega, which is made by the South Korean company Coway, and think it works efficiently and quietly to reduce indoor air pollution, but it comes at a price that some may not be able to afford. The full price of the Airmega 300S can be over $700, and the 400S can be over $800, but in the golden age of the internet, nobody pays full price anymore, amirite? The company itself offers discounts on the units (view on, and Amazon listings are similarly priced. That's not counting the costs of filters, which should last up to a year, and the non-Wi-Fi models are priced for less than the S models.

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Disclosure: The writer received a review model of the 400S from Airmega, but all opinions, errors, or omissions in this review are the writer's alone.