Coway Airmega 400S Air Purifier – Review

The Coway Airmega 400S is an outstanding air purifier intended for rooms up to 1560 sq. ft. It is, without a doubt, a powerful beast, with huge power and brilliant air cleaning performances.

Coway AIRMEGA 400S Air PurifierCoway AIRMEGA 400S Air Purifier

The real treat in the Airmega 400S is the Smart Sensor. You can easily monitor the room air quality in your apartment with a simple light ring on.

A LED screen will display the current air quality in the room. When the air is good, it will turn positive, and when it is terrible, it will turn negative.


Manufacturer Coway
Model Airmega 400S
Dimensions 14.8 x 14.8 x 22.8 inches
Filters Pre-filter, Green True HEPA Filter and Activated Carbon Filter
Coverage 1560 sq. ft.
Warranty 5-year
User manual PDF

Airmega 400S Features

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Feature Info
Air Quality Monitoring Coway Airmega’s pollution sensor communicates indoor air quality in real-time. The brightly colored LED ring lets you know how clean or dirty your indoor air is every minute of the day.
Smart Technology With its Smart Mode feature, the Coway Airmega automatically adapts to its surroundings by adjusting fan speeds based on the room’s air quality.

Such a fantastic air purifier has many features. Many of the features are highly advanced technology which you can hardly find at other air purifiers.

True HEPA Filter

The powerful True HEPA filtration system guarantees the purity of the fresh air in the room. This system is capable of trapping 99.97% of airborne particles, including allergens, mold spores, bacteria as well as viruses. This is the highest level of cleaning a home can have.

The True HEPA filter is an excellent choice for an air purifier filtration system if you are looking for ways to remove allergens from the air. As already mentioned, pollen, dust, mold spores are significant allergens, and many people get allergic reactions if exposed to these particles for a prolonged period.

Carbon Activated Filter

This filter can remove gases, smoke, and even dangerous poisonous gases from the air. Gases are hazardous to your health and at high levels can be deadly. This system is perfect for places with lots of bad odor. Bad odors like pet pee, onions, smoke, and even sweat can be removed with an activated carbon filter. Thanks to this filter your home will smell fresh and the whole air will appear like it just comes from a fresh mountain top.

Real Time Pollution Sensor

Advanced technology like that of air purifiers is quite rare. An average air purifier simply doesn’t have the sensor that detects even the slightest increase in the particles in the air. As a result, you will still experience fresh air no matter where you place the air purifier.

Once the Coway Airmega 400S air purifiers detect a high level of air pollution, it will turn the LED ring on the air purifier to red color.

The red color means that the air quality in the room is very unhealthy.

If the ring turns color to yellow, that means that the air is polluted and unhealthy and you should as soon as possible turn the air purifier either to automatic mode or turn the speed on.

The green color indicates that the air quality is moderate and that you should keep an eye on the indicator if it moves to a good state or an unhealthy yellow state.

The blue color is the color you want to see all the time on the air purifier, and that simply means that the air in the room is good and healthy.

Smart Auto Mode

The Coway Airmega 400S uses air quality sensors, so why not use that sensor to automatically adjust to the level of pollution by turning the air purifier to auto mode.

On auto mode, the air purifier will monitor air, and as soon as the quality of the airdrops, it will adjust the speed of filtration. With the Airmega 400S, you can save money on not running the air purifier at maximum capacity when the air is good. 

Dual Suction

Coway Airmega 400S has a powerful air intake from both sides. Then the magic of air filtration is done in the middle of the air purifier, and fresh, clean air free from particles and allergens is released on the top of the air purifier. With such a suction model, you can place this air purifier near the wall where it won’t bother anyone, just make sure you don’t place it in the corner because then one suction side will not work correctly.

Filter Indicator

Max2 Filter is the name of the primary filter in the Airmega 400S which is built from True HEPA filter and deodorization filter known as an activated carbon filter.

The air purifier monitors the Max2 filter, and as soon as the filter gets unusable, the air purifier will tell you to replace it.

The pre-filter is also included in the filtration system. You should periodically clean the pre-filter with a vacuum cleaner or maybe even use water to clean it properly. If you do use water, then make sure that before placing the pre-filter back in an air purifier is completely dry.

The good news is that there is also an indicator that will tell you when you need to wash pre-filter. This will save you lots of time by not washing the filter when it is not required.

Designed for Room

Make sure that visitors or young children don’t mistake this air purifier for a table and place some stuff on top of it because that will not be good for releasing the fresh air back into the room. The boxed shape on four legs can make people mistake this air purifier for a table or small piece of furniture. As long as they understand that this is actually an air purifier, there is no problem, and such design just proves that this air purifier can fit any room.

IoCare Mobile App

For advanced usage and to lift the air purifier to a whole new level is the IoCare application made by Coway for their air purifiers. For now, only 400S and 300S can use advanced options that this application offers but in the near future other models will be added. On the app, you can from any place on the earth monitor and manipulate the air purifier as long as you have access to the internet. 

For real science fiction usage, you can use Amazon Alexa to control the air purifier with your voice. Dash replenishment service is also available to the users that use the IoCare application. We can say, without a doubt, that Airmega 400S is a smart air purifier.

Five Modes

On the lowest speed, the noise level is entirely silent, and you can sleep with the Coway Airmega 400S turned on without a problem.

In case you need to use other modes than sleep mode, you can choose that on the air purifier options panel. High speed is the highest achievable filtration rate, and this high-level air purifier is making 43 dB. The smart mode mentioned above is a highly recommendable option to use. With this mode, you can save money but as well keep the room at the best air quality level.


The timer is adjustable, and you can choose between 1,2,4, and 8 hours of continuous filtration. This option is very good to use when you can forget that you have turned the air purifier on. Simply always use this option, and your air purifier will not work when it is not supposed to work.

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Filter Replacement

Max2 filters need to be replaced every 12 months. The price for the combo filters of True HEPA and carbon filters is not small, and you should know that before you decide to buy this product. The maintenance cost on this air purifier is a bit higher than on other lower or mid-range air purifiers.

But you should also keep in mind that this air purifier is capable of filtering extremely large rooms of 1560 square feet. In other words, this air purifier alone can be used as a filtration system for a whole apartment. 

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Feature Info
MAX2 Filter Technology The Max2 filter – a combined activated carbon and a True HEPA filter—captures and reduces up to 99.97 percent of particles 0.3 microns in the air, including pollen, pollutants and other allergens.
Green True HEPA Filter Traps 99.97 percent of airborne particles up to 0.3 microns in size.

Replacing filters is easy, and it should not present a significant problem for anyone.

Airmega replacement filters are made of high-quality material, and all you need to do is put them in the air purifier, and that’s about it. The pre-filter is not replaceable, but in case it gets destroyed or broken by the constant washing, you can order that filter too.

The pre-filter is much more affordable than the Max2 combo filter.

Pros and Cons

To revise, here are the advantages and disadvantages of the Coway Airmega 400S air purifier:


  • Useful in Extremely Large Room
  • Smart Sensors
  • Auto Mode
  • Mobile Application
  • Interesting Design
  • Good for Allergies
  • Good For Asthma Patients
  • Powerful
  • Energy Star Efficiency


  • When an air purifier gets packed with so many fancy options and advanced technology, it is pretty normal that the price you need to pay for it is not small. Because of that that is the only disadvantage of this air purifier, it is not available to all people because of the budget wall.

Final Thoughts

The Coway Airmega 400S is not affordable air purifier, but those who have the budget to buy it will enjoy the fresh air that this device release.

It can cover a huge room, and by that, it can be used as the main filtration system for a whole home. When you put things down like that, then you can say that even though you are paying a higher price for this product you are getting back a lot.

Many owners of Airmega 400S will agree with me, and I hope they put a good word about this air purifier below in the comments section.

Update Log

August 11, 2021 – I have improved the article design, added specifications, and rechecked some information about the product.


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