Bests & Worsts Reviews from Amazon

Disclosure: I am a long time Amazon Prime member, but purchased my 400S from an online retailer that specializes in air treatment equipment because of better pricing and was for sure an authorized dealer (buying from unauthorized dealers usually means no warranty coverage - I have read on other reviews about this problem with some Amazon sellers). I am reviewing here at Amazon because hopefully it will help more people. I have this unit placed in our main living room where the family spends the most time in an effort to help my wife with asthma symptoms which have worsened over the past 6-9 months. In the past I have been skeptical of the effectiveness and need for air purifiers (my wife has not had any real symptoms for years), but since installing the air purifiers (I now have this unit, plus 1 other brand in the master bedroom and yet a different brand upstairs) my wife has been breathing easier and with less need for her inhaler medication. So now I am a believer. When evaluating air purifiers, I looked closely at the published air flow rates vs sound level for each fan speed. My goal for this unit was to have constant air purification with noise levels that would not be too obtrusive with normal conversation and TV viewing in the living room. For air purification to be effective there must be an adequate number of air changes per hour (ACH) at whatever fan speed you can tolerate. Based on my research, the recommended ACH seems to be in the 4 to 6 air changes per hour range for effective particle reduction. (FYI: the Blueair website has a Performance Book that has a good graph of room particle reduction vs air changes per hour that shows that around 4.5 to 5 ACH the particle reduction is around 90% and the point of diminishing returns has essentially been reached.) My filter placement is 4-5 ft behind the couch, so my preferred noise level is 48-50 dBA or less while watching TV, etc. Airmega only publishes a noise range of 22-52 dB (which I assume is dBA) for the 400S and room coverage of 1560 sq ft at 2 air changes per hour. The Airmega published room coverage data (based on 8 ft ceiling height) lets you calculate the maximum air flow as 416 cfm at the highest speed, which is a pretty decent rate when compared to other premium air filters. I have checked the 400S operation with an iPhone sound level app (NoiSee) and a portable anemometer and measured the following data for the fan operating range: Sleep 64 cfm 22 dBA (this is essentially silent and that is actually Airmega noise value - the app won't read that quiet) Speed 1 115 cfm 32 dBA Speed 2 286 cfm 46 dBA Speed 3 427 cfm 54 dBA (slightly higher than Airmega "Certified" level - but they don't specify dBA scale) For me these operating characteristics work quite well. Our living room is roughly 337 sq ft, so at Speed 2 we get a continuous ACH of 6.4 and a sound level that is perfectly tolerable. My operating schedule is to have the purifier at speed 2 from 5:30am to 11:30pm, then run at speed 3 from 11:30pm until 5:30am for maximum cleaning during the night while everyone is asleep. Hopefully I am drawing some air from additional rooms at the high speed since the living room is open to other areas of the house of course. I find the quality of the 400S quite good. The housing is plastic of course, but it is a good thickness and quality. The unit is reasonably sized and aesthetically pleasing, although for me the looks are secondary to functionality and performance. The 2 HEPA filters fit snugly into the housing and have a foam seal around the filter perimeter to ensure that all air passes through the filters with no or minimal by-passing. The filters also have a thin layer of activated carbon for some smoke and odor reduction, but I am a bit skeptical how effective that will be due to the carbon layer thickness. Fan operation is very smooth and I like the air flow pattern of the 400S, drawing inlet air into 2 sides through 2 separate filters, then discharging clean air upwards toward the ceiling. This achieves 2 things - there is minimal draft produced so you do not have air blowing on you constantly, plus the clean air is forced to the ceiling where it can travel across the room, circulate down the opposite walls, and sweep air back towards the unit for more effective cleaning. The dirty inlet air and clean discharge air flows are also separated as much as possible, which should reduce the amount of short-circuiting of clean air back into the unit which in my mind should increase the overall cleaning effectiveness. The unit could be quieter if the discharge air outlet were a bit larger, but that would also make the unit bigger and reduce the outlet air velocity thus reducing the effectiveness of the air flow pattern stated above. This unit seems to have a good compromise between quietness and air flow. The controls are intuitive and on the 400S are touch sensitive. The lighting of the unit does not concern me in our application, but can be turned off in a bedroom application. The filter operation lights are on top and should not be a problem, but the air quality light is fairly large and could bother some folks. Other reviewers are correct in that it chimes with every operation and I have not found a way to silence it, so that may also be a consideration in a bedroom application. I have not tried the Sleep or ECO modes - mainly because of room placement, but I also want the purifier to be actively cleaning the air at all times. A plus to me is that the air quality light continuously shows the measured air quality while in manual speed control operation, not just while the unit is in Smart Mode to adjust fan speed based on air quality. I guess I should really test that function just to ensure correct operation with my unit for possible future use, but I am sure it will work fine. The iPhone app took 2 attempts to initially connect with the 400S, but since then has operated flawlessly - but it has only been a week. I have the app installed on my iPhone and iPad Mini 2 and both are running iOS 10.2.1. The app could use a bit of work in that it does not appear to be connected at all with the Airmega website even though I use the same email address for both. I entered my registration information, including place of purchase, purchase date, model & serial number of purifier, etc. in the iPhone app and got a message that the info was successfully transmitted yet my account on the on-line website gives no indication that I have a registered unit nor does it have a way to enter that information. It only has a section to show orders made directly through Airmega. I guess that I will have to make a phone call to Airmega to confirm registration and that my 5 year warranty is in force. A bit of an unnecessary hassle. The app functionality is OK. You can perform basic manual control (power on/off, lights on/off, check filter life). It also has a section to set up an operating schedule. I have mine programmed to set the unit to fan speed 2 every day from 5:30am to 11:30pm and change to fan speed 3 from 11:30pm to 5:30am on Sunday thru Thursday (I left Friday and Saturday nights off that schedule since we may be watching movie, etc. later than on work nights). I found that when the unit is operating by the schedule function you have to define every hour of the day or else the unit will power down during undefined times. For example, the above schedule did not define operation on Friday or Saturday night after 11:30pm so the unit shut down at 11:30pm. I intended for the unit to continue at fan speed 2 after the daily 5:30am to 11:30pm schedule finished, but instead it powered down. So I had to enter a 3rd schedule to operate at fan speed 2 from 11:30pm to 5:30am on Friday and Saturday night.. Not a big deal. So far the scheduled operation has performed without fail. And contrary to some other reviews, if the app does not work then the only real loss is the scheduling feature and air quality data logging. All of the basic functionality of the unit can be controlled on the unit itself manually. Other useful features of the app is to set the Smart Mode air quality measurement sensitivity (high, medium (default), low), set pre-filter wash frequency notification time (2, 3, or 4 weeks), set time zone (for schedule operation presumably). You can also set up notifications to your phone for filter life milestones (pre-filter life reaches 0%, HEPA filter life reaches, 10%, 5%, 0%), for Indoor Air Quality alert (level reaches "Very Unhealthy"), and any system errors or failures. The app also logs the Indoor Air Quality measurements continuously and the data can be displayed on a circular graph that give % of time at each level, or displayed on a standard Air Quality vs. time line graph. You can display 4 different time spans - the last 24 hours, last 7 days, last 30 days, or last 12 months. One thing that confused me at first was that in the "last 24 hour" view the line graph shows spikes in air quality (poor quality is higher on vertical scale), yet when I look at the "last 7 day" view their is only relatively low spikes shown. That is because the 7 day, 30 day, and 12 month views display the average air quality. Since the air quality is usually "good", the daily average shows just moderate excursions. I guess the utility to this section of the app would be to possibly identify any recurring patterns of poor air quality that could be tied to events one could change (if your air quality is primarily good). Or it could prod one for indoor changes if air quality is routinely not so good. Otherwise it is just interesting information. I know this has been long and rambling, but hopefully helpful to some. All things considered, I find that this purifier will suit our needs very well and is a keeper. It has good air flow / noise levels, the HEPA filters seem to be good quality, HEPA filters seem to be on-track for approximately 1 year life based on my operating schedule (I am at 98% life left after 1 week), good overall size and aesthetically pleasing to me, and Coway is a long time South Korean manufacturer with good track record for quality products and product support. Only time will tell on the overall quality and longevity of this particular model.