Coway Airmega 400 Review

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Updated January 11, 2023
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92 Expert Rating

Finding the best air purifier boils down to your personal use: do you want the best whole house air purifier or the best large room air purifier? The Coway Airmega 400, for example, has traits from both, handling more air in one hour than many similarly priced purifiers can in two.

Why We Like It – Coway Airmega 400

The Coway Airmega 400 is what you turn to for larger-than-life rooms, thanks to its 1560 square feet of coverage. It’s also incredibly energy efficient, automatically adjusting the fan speeds so as to not use more energy than needed.

  • Covers up to 1560 square feet
  • Smart Mode adapts fan speeds
  • Air quality monitoring
  • Filter replacements are pricey

Power & Speed

As far as power is concerned, the Coway Airmega 300 is pulling 64 watts of power. To put that in perspective, some light bulbs actually use more power. And yet the Airmega 300 does what it does with as much or less power, similar to the Coway AP1512HH. There are four speeds to choose from, but with Smart Mode, they can adjust automatically.


That kind of power translates to pretty wide coverage. It feels most comfortable in a room no bigger than 1560 square feet, which is three times the coverage that the Dyson TP04 Pure Cool Tower can achieve. Anything more and its 400 CFM rating will begin to suffer. But what’s crazy is the Alen Breathe Smart Classic Large Room Air Purifier covers just 1100 square feet, yet it’s $100 more.


Where some purifiers use three stages of filtration, the Coway Airmega 400 uses 2—well, more like 2.5. That sounds like it’s less efficient, but it actually combines filters rather than split them apart. Particles come up against pre-filters first, then the activated carbon green True HEPA filter Coway Airmega combined. Carbon filters and HEPA filters are usually separate, but are combined with the Max2 Filter set. Both are washable pre-filter Max2 filters. Most particles as small as 0.3 microns will be captured. If this were the Medify Air, however, it would’ve gone through a 4-stage filtration system, rather than 2.5 stages.

And, for those who need to know how often to change the air purifier filter, our guide can help you find out the right times.


Just like the Blueair Classic 605, take one good look at the Coway Airmega 400, and you’ll know it’s pretty sturdy. Its entire body is made of thick plastic, so it’s lighter yet durable, and has four legs protruding from the bottom. These will ultimately give it better stability if someone bumps into it, unlike the Honeywell True HEPA air purifier, which doesn’t seem very sturdy at all. So, if you want a unit you can hide behind a couch, then visit our Hamilton Beach 04531GM review.


Despite being slightly outperformed by a handful of purifiers in this price range, the Coway Airmega 400 offers more than performance. It’s still worth every penny, but sweetens the deal by being app-enabled, so if you have Wi-Fi, you can get notifications for when the HEPA air filters need replacing. The Oransi Max HEPA Air Purifier is cheaper, but only covers half as much square footage.

Coway Airmega 400 Wrap Up

The Coway Airmega 400 doesn’t just offer power and efficiency, but also ease of use. Yes, it covers up to 1560 square feet, but it’s also very hands-off. It has a filter indicator to show you when to change the filters. And its power consumption is curbed through automatic adjustments to the fan speed. However, filters can get a bit pricey.

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