This $360 smart air purifier is quieter than a computer and turns on automatically when it senses polluted indoor air in my home

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Coway/Facebook

This isn't my dining room, but look how well the air purifier fits into this setup.

• A high-quality air purifier filters out the irritants in your room or house, runs quietly, and has reasonable long-term costs.
• I like the Coway Airmega 400 Smart Air Purifier because it can operate and self-adjust fan speed based on the air's pollution level, and when on the lowest mode, you can barely hear it running. Plus, it actually looks attractive in my dining room.
• Though it's one of the most expensive options out there (currently starting at $361.24 on Amazon), there's a five-year limited manufacturer's warranty for the motor and electronic parts.

When your home is inundated with smoke, dust, pollen, pet hair, and other debris, it only makes sense to look for a way to improve your indoor air quality. While regularly vacuuming, cleaning your HVAC filters, and banning smoking in your home can drastically improve your indoor environment, many of us don't have to time or the patience to do any of those things on a daily basis.

This is where a high-quality air purifier can help.

I've been using the Coway Airmega 400 Smart Air Purifier, a new model from one of the top names in the air purifier industry for the past three decades,

Read more: The best air purifiers you can buy

Specs

Coway

The Coway Airmega400 can the air in 760-square-foot room in around 15 minutes.

The Airmega 400 is available in white and graphite/silver. I tested the graphite model, which fit in well with the darker tones of my dining room. The unit is 23 inches high and 15 inches wide and deep so it takes up a little bit of room, but doesn't dominate the space. For the most part, when guests visited, they didn't notice it was there, and if they did, they thought it looked fancy.

The unit weighs 25 pounds so it isn't ideal for lugging around to purify the air in each room of your house. However, it does have handles on each side if you do decide to move it.

Here are some other important specs:

• Coverage: 24,960 cubic feet per hour. Put another way, it can clean the air in a 28-foot by 28- foot room with an 8-foot ceiling four times in an hour.
• Filters: Washable prefilter and Max2 filter set, which is a single filter featuring True HEPA and activated carbon components.
• Rated Voltage: 120 V~ 60 Hz.
• Power: 66 W and Energy Star-certified.
• Timer: You can set the air purifier to turn off after one, four, or eight hours.

Set-up process

Setting up the Airmega 400 was incredibly simple. Basically, I removed the packaging, plugged the purifier into a power outlet, and it went to work. The whole process took about 15 minutes.

Before turning the Airmega on, you need to be sure to remove all of the plastic from the two Max2 filters on each side of the unit. This is an effortless task that helped me familiarize myself with the device. The instructions are spelled out in the helpful user manual.

When you first turn on the unit, it's automatically set up to run on Smart Mode, which I'll cover in more detail below. If you'd prefer a different mode, there are three air speeds to choose from and you just run your finger along the touch sensor to choose the mode you want; I just keep mine on Smart Mode.

Read more: How to test and improve the air quality in your home - because indoor air is shockingly worse than outdoor air

What makes the air purifier stand out

I can only relay anecdotal evidence for how well the Airmega 400 cleans since collecting hard data would require a high-quality handheld particle counter, which costs thousands of dollars and I'm not going to try to convince my editor that the cost is justified. However, Consumer Reports performed a test on the smaller Airmega 300 and found it did an excellent job of removing dust, pollen, and smoke when running on high in a large room.

Based on my subjective experience, the Airmega 400 did a terrific job of clearing the air and it's insanely quiet. When the Airmega 400 is on its low setting, the only way to tell its running is by putting your hand over the air vent to feel the breeze. From four feet away, my sound meter registered 39 decibels. That's quieter than a computer. With the fan on high, the sound meter read 55 decibels, which is still quieter than your average conversation.

The main times I actually noticed it working was when I was doing intense frying in the kitchen, my wife was vaping inside, and I was burning incense. When the purifier's pollution sensor recognized the irritants, I would see the LED change from blue (which is good) to red (which is unhealthy) and the fan would ramp up. During testing, my sensitive smoke alarm never went off and the visible evidence dissipated within a few minutes of us finishing our smoky pastimes.

I appreciate that the Airmega 400 is Energy Star-certified and features a Smart mode. When in Smart mode, the fan automatically stops after 10 minutes of low pollution levels. If it detects pollutants in the air, it automatically starts up until the levels indicate good air quality again. This helps you save on electric bills.

Cleaning and maintaining the Airmega 400 is simple. The filter indicator lets you know when it's time to clean the pre-filters, which is about every two weeks depending on the pollution levels in your home. I just run my hand vacuum over them to remove the debris. Coway also recommends that you wipe down the vents and pollution sensor with a soft dry cloth every two months.

Cons to consider

The biggest expense with an air purifier is replacing the HEPA filter. Airmega 400's replacement filter set comes with two filters but is currently $122.50 on Amazon, so it can be pricey for some. Fortunately, you only need to replace the filters every year or so.

An air purifier should not be your first line of defense against indoor irritants. Instead, it should be minimizing activities that contribute to air pollution, such as indoor smoking, using candles, burning wood, and storing chemicals and solvents inside your house. Maintain your HVAC equipment, vacuuming, and changing or cleaning air filters regularly can help keep indoor air clean, especially if your vacuum has HEPA filtration.

If you're still having air quality problems, then an air purifier may be in order.

The bottom line

Amazon

It's also really quiet when on the lowest setting, which is still quite powerful.

Overall, I was impressed with the Airmega 400. Even though it's spring and pollen counts are rising, I'm sneezing less and my eyes are less irritated than usual. The Airmega 400 does an excellent job of clearing up vape clouds, smoke, and dander. Best of all, because it's so quiet, I rarely even notice it's even operating.

Should you buy it?

I would strongly recommend the Airmega 400 if you have 1,500+ square feet of indoor space where you want to improve the air quality.

What alternatives are there?

• The Airmega 400S is almost exactly like the 400, but you can use it with the Airmega IoCare app to monitor indoor and outdoor air quality, get notifications when you need to clean the filters, schedule when the purifier is running, control fan speed, and pair with Alexa.
• The Airmega 300 and 300S are slightly smaller versions of the 400 and 400S. They filter the air in a 628-square-foot room with an eight-foot ceiling in 15 minutes.
• I've tested the Mighty, which is Coway's most popular model. It's smaller than the 400 and cleans the air in a 503-square-foot room in about 15 minutes. And, at 12.3 pounds, it's quite portable.
• I also tried out the new Airmega 200M, which is an update to the Mighty. It purifies a 540-square-foot room in 15 minutes and is about the same size as the Mighty.

Which model should you get?

If you have a large space you want to remove irritants from, I'd recommend the Airmega 300 or 400. If you just have a smaller space or want to be able to move the air purifier with you from room to room, then the 200M might be your best bet. And, if you want your purifier to be part of your smart home set-up, consider the 300S or 400S.

The Coway air purifiers do an excellent job of attacking indoor pollutants, and I'd highly recommend any of them.

Pros of the Coway Airmega400: Runs quietly, cleans the air in a 760-square-foot room in 15 minutes, energy efficient, attractive design

Cons: Expensive replacement filters

Buy the Coway Airmega 400 Smart Air Purifier on Amazon starting at $361.24 (originally $749)

Buy the Coway Airmega 400S Wi-Fi Enabled Smart Air Purifier on Amazon starting at $459 (originally $636.99)

Buy the Coway AP-1512HH Mighty Air Purifier on Amazon for $161.95 (originally $229.99)

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