Airmega 400 HEPA Air Purifier
The Coway Airmega 400 model features smart mode (auto, sleep, eco) and real-time air quality monitoring, so you can rest assured that your air is being cleaned at all times. The Coway Airmega 400 is designed to accommodate room sizes up to 1,560 square feet and it cleans the air two times in one hour. Coway Airmega draws contaminated air from two sides and pushes filtered air out the top of the unit, cleaning the air you breathe faster and more efficiently. The air filter indicator tells you when the two Max2 filters need to be replaced, and the pre-filters need to be cleaned for maximum efficiency, based on how much air they have processed. The easy-to-clean pre-filter captures large particles like hair, fur and dust in its micromesh, so Max2 filter can work more effectively. The Max2 filter—a combined activated carbon and a Green True HEPA filter—captures and reduces up to 99.99 percent of particles 0.01 microns in the air, including pollen, pollutants, and other allergens. It also reduces more than 99 percent of volatile organic compounds and reduces fumes such as NH3 and CH3CHO. With its Smart Mode feature, the Coway Airmega automatically adapts to its surroundings by adjusting fan speeds based on the room’s air quality. That means your unit is energy efficient without compromising efficacy. When the air quality in the room remains purified for 10 minutes or more in smart eco mode, Coway Airmega turns the fan off to conserve energy. When Coway Airmega’s built-in light and pollution sensors detect that the room has been dark and the air is clean for three minutes, Coway Airmega reduces noise and power consumption. 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.
Why r/BuyItForLife recommends it
10 mentions from real owners
- #1Dec 30, 2025
Best Air purifier to reasonable price? for Smoke and garbage smell
Is your apartment a condo, or is it in a house and share an HVAC/air handling system with the unit causing the problems? If you are in a condo apartment, new weatherstripping around your door/door frame, and a new door sweep can drastically reduce the amount of contaminants/bad smells entering your unit, and will be needed if you decide to use an ozone generator. Be very cautious with ozone, as it can trigger asthma attacks, as well as causing permanent lung damage. I would only use it on a timer, and be out of the apartment for the **whole time**, and only go back to the apartment after **at least** four hours after it has switched off, and then only to open all the windows for another couple of hours. Depending on the size of your unit, I would likely suggest the Coway Airmega 400. It's better to have an oversized unit, which you can run on a lower speed setting, rather than a smaller unit running on max, because of the noise. **Never** buy an "air purifier" with ozone, as it will trigger asthma attacks, and damage your lungs. Ozone is highly reactive, and does not distinguish between smoke/organic smells and the extremely delicate tissues that line your lungs.
View on Redditopen_in_new - #2Dec 30, 2025
Best Air purifier to reasonable price? for Smoke and garbage smell
Is it coming from outside, or like seeping through the walls from other apartments? I moved into an older apartment a few years ago and was getting a lot of cigarette smoke coming through the walls. I did some strategic sealing up of outlets and cracks which helped some. Then I got monster air filter (Coway 400) which helped a little more. What really helped was when I got some stuff from A/C Infinity in order to bring filtered fresh air into the apartment, essentially to pressurize it slightly and to push our air out through the cracks instead of allowing their air to come in through the cracks. It does have some gaps around the window kit, and in the summer in brings in wet/hot air (cold/dry in the winter) so it increases your electricity/HVAC usage a little, but for me it was worth it and cheaper than breaking the lease and moving again. Air fan kit [https://www.amazon.com/AC-Infinity-Filtration-Ventilation-Hydroponics/dp/B09NXKGK89](https://www.amazon.com/AC-Infinity-Filtration-Ventilation-Hydroponics/dp/B09NXKGK89) Filter box, you can replace with MERV 14 filters when this one gets plugged up [https://www.amazon.com/AC-Infinity-Inline-Filtration-Ventilation/dp/B0921N33Y7](https://www.amazon.com/AC-Infinity-Inline-Filtration-Ventilation/dp/B0921N33Y7) Window duct kit [https://www.amazon.com/AC-Infinity-Universal-Ducting-Conditioner/dp/B0BTFDTWK1](https://www.amazon.com/AC-Infinity-Universal-Ducting-Conditioner/dp/B0BTFDTWK1)
View on Redditopen_in_new - #3Nov 4, 2025
The Best Air Purifier for Home now? Have you noticed a huge difference since you started using them?
Coway 300/400.
View on Redditopen_in_new - #4Nov 3, 2025
Best HEPA Air Purifier for Home?
A few people have recommended Coway and I agree. We have the older version of the Airmega 400 and its great; I bought it in 2018 and it is still working perfectly. No it isn't super quiet on the highest speed, but we keep it all the time on the "smart" setting so it kicks on when it needs to. Our current space is about 800 sq ft and it's rated up to 1000 sq ft. I've had it running basically non-stop on the "smart" setting since we moved to our new place in January, we put new filters in and they are about a month away from replacement. We have to clean the pre-filters every month or so, and I vacuum out the exposed sides of the HEPA filters every time I do that. The filters are expensive because they are real HEPA, you can buy knockoffs, but honestly I buy the Airmega branded ones.
View on Redditopen_in_new - #5Nov 1, 2025
Best air purifier for home
Smart Air Blast MKII or Blast Mini, Coway Airmega 400.
View on Redditopen_in_new - #6Aug 8, 2025
Need Help Choosing the Best Air Purifier for Allergies, True HEPA and Quiet
Directly from Austin Air Canada, the CADR(Clean Air Delivery Rates) and decibel levels, both of which they don't tell you on their site, last time I checked: "The CFM by speed is: High 250, Medium 125, Low 47 Decibel levels by speed are: High 62, Medium 52, Low below 50 If you need further assistance, please reach out to Austin Air Canada at 888-236-9525 or customerservice@austinair.ca" Compare that to the Coway Airmega 400, which (from elsewhere on reddit and other sources) tops out at 52dB on high. Decibels are a logarithmic scale, so the 62dB of the Austin Air is **ten times** as loud as 52dB from the Coway 400. The CADR of the Coway Airmega 400 is 400cfm for pollen (source: US Gov EnergyStar program: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjXuOu49pCGAxXOhf0HHTIRAYgQFnoECCgQAQ&url=https%3A%2F%2Fwww.energystar.gov%2Fsites%2Fdefault%2Ffiles%2FRoom%2520Air%2520Cleaner%2520Draft%25201%2520Version%25202.0%2520Data%2520and%2520Analysis_0.xlsx&usg=AOvVaw0G-z9wF5ZtF2Gu3KSm1rqA&opi=89978449 ) So, if you want a HEPA filter that is 10 times louder, 40% less efficient, and more than twice the price, then buy the Austin Air, otherwise Coway or pretty much any other HEPA filter is a better bet than the Austin Air. My daughter's school was forced to buy them, and on high they make even ordinary conversation impossible, let alone teaching. Hot. Garbage. Look at Airpura if you want a truly BIFL whole-house option.
View on Redditopen_in_new - #7Aug 8, 2025
Need Help Choosing the Best Air Purifier for Allergies, True HEPA and Quiet
Austin Air is overpriced, and sounds like a jet aircraft taking off. For contrast, look at the Coway Airmega 400, or the Airmega400S (for "Smart") if you want detailed sensor readings/remote operation. For that size room, you could even start with the Coway AP-1512HH and then add a second unit if the one wasn't enough.
View on Redditopen_in_new - #8Apr 11, 2025
The REAL best air purifier - I HATE DUST!
Coway Airmega 400! Love mine. And looks great. Don’t need the 400s version.
View on Redditopen_in_new - #9Apr 11, 2025
The REAL best air purifier - I HATE DUST!
I have 5 Coway Airmega’s. 1x Airmega 250 3x AP-1512’s 1x Airmega 100 They are BY FAR the best I’ve ever had and I recommend them to everyone. There was a very thorough test video done by wire cutter that originally piqued my interest here: https://youtu.be/VM9CJZpqfpA?si=s45QTvHQnlvtbcDE
View on Redditopen_in_new - #10Apr 9, 2025
The Best Air Purifiers?
I started with the HATHASPACE HSP003 when the smoke rolled in and it handled ash and odor in my living room pretty well. After a few weeks I needed something for my open‑plan space, so I upgraded to the Coway Airmega 400.
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