Coway Airmega 400S Review

The main draw for the Coway Airmega 400S is the unbridled power it possesses. It'll be really tough to find another air purifier that can outdo this one in terms of pure performance. It has incredible coverage and should prove adequate in nearly any space up to about 3,120 square feet. Continue reading to find out just how well it did in our comprehensive testing process.

Performance Comparison

Air Cleaning Performance

The Coway Airmega 400S is a class leader in our air cleaning performance analysis. Few models can filter air as thoroughly and at such a high rate while at the same time reducing odors such as smoke in the process. Not surprisingly, this unit has one of the highest Clean Air Delivery Rates (CADR) in its class which was supported by our independent assessment using a Dylos air quality monitor.

Our analysis of air cleaning performance is simple yet sophisticated and comprehensive. We burned sheets of paper in a tin-foil-lined bowl to bring the Dylos Air Quality Meter particulate reading to approximately 500 AQI (around 35,000 large particles). We then turned on the purifier and recorded the time it took to clean the air. The 400S reduced the particulates to 49 in 30 minutes and down to an impressive two particles in 45 minutes. The 400S also has a robust CADR. While many manufacturers list the CADR in a single number, the 400S breaks this rating into three relevant categories. These categories and their ratings (in cubic feet) are as follows: smoke (328), dust (328), and pollen (400). All told, the Airmega 400S removed 100% of particulates in the allotted 60 minutes.

Another key component of air cleaning performance assessment is the odor reduction analysis. Burned paper used in this evaluation produces small molecules that are the source of the perceived smell. Removing these molecules from the air is quite difficult as they are often too small to be captured by the purifier's filter. Despite the difficulty of this task, the 400S did quite a bit better than other models in the class, though there was still a slight acrid smell left behind in the room at the end of the hour-long testing interval.

As a final note on air quality, this unit has a built-in sensor that automatically turns on the machine when air quality falls below a certain threshold. While this feature is not a rated component in this assessment, we thought it was a nice touch worth mentioning.

Noise

No one wants to trade air pollution for noise pollution. As such, we assess the volume and pitch of the noise produced by the purifiers under our review. While the Coway Airmega 400S is not the quietest model in the class on high or medium settings, it's ultra quiet on low. Moreover, the pitch is relatively natural and easily goes unnoticed. This assessment is all the more impressive when one considers how much clean air this machine moves and the size of the motor and fan required to do that work.

Our assessment of the noise produced by the air purifiers is measured by a sound pressure monitor (measuring decibels) and our ears. The sound pressure monitor measures the noise produced by the machine at six feet, while our ears assess the pitch of the motor and fan as it's not just the volume but also the kind of noise that is being produced that can be distracting. We assess the machine's volume and pitch at low, medium, and high settings.

The 400S also has a sleep feature. For those who are extremely light sleepers, be aware that this machine kicks into an ultra-quiet “sleep mode” when the room it's in becomes dark and the air quality is sufficiently high. This setting is so low that you can hardly hear it running.

Ease of Use

The two most important things an air purifier does are remove particulates from the air and do so quietly. However, once those aspects are satisfied, the device should also be easy to use. While not the easiest purifier to use in its class, the 400S is not tough to figure out. To evaluate the ease of use we look at the device's setup time, interface (remote and on-unit controls), customization (air-quality sensor and settings), and portability (dimensions, carrying handles, and weight).

The 400S is a breeze to set up, requiring less than five minutes from boxed-up to fan spinning. The unit also has an app that acts as a remote control. The app is easy to navigate; however, it is largely unnecessary because the onboard controls are well laid out and intuitive, with a touch slider for speed settings and lights indicating both settings and air quality. However, all this is moot because when the unit is set to the “smart” mode, it will turn itself on/off depending on the air quality. Finally, the 400S is on the larger and heavier (24.6 pounds) end of the spectrum for air purifiers in our review. While it isn't advisable to travel with this unit, its carrying handles make it fairly easy to move around the house.

Operating Cost

In our operating cost testing, we determine the operating cost of an air purifier by using the national average kilowatt-hour rate of $0.13, and we assume a daily usage of 12 hours per day. We also include the cost of the filter replacement based on the manufacturer's recommendations and the cost of the purifier itself. Finally, we assume a five-year life of the device, so the unit's cost is divided over the first five years.

When it comes to larger appliances — especially those that run for long periods of time — operating costs are a real concern both in terms of maintenance and power consumption. While the power consumption of the Coway Airmega 400S isn't excessive, considering the amount of air the unit can move, its filters come at an eye-popping $129. In the 400S's defense, it does use a true HEPA filter (the gold standard for air purifying filters). However, this defense only goes so far. As such, the long-term cost of this unit is among the highest in the class.

Should You Buy the Coway Airmega 400S?

Looking at the upfront and long-term cost of the 400S alone, it would be easy to say that this unit offers consumers a poor value. However, for the right user, the cost will pencil out. This unit is great for big spaces and outperforms the competition in this regard. So, if you have a big indoor space that you want to keep particulate-free, this machine will be well worth the high cost.

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