Coway Airmega AP-1512HH(W) True HEPA Purifier (Open Box)

I'm not sure how this is so highly rated. Although it does work, more or less, for the price it really has many issues of poor design. Some of the features you are paying for are useless because of the way they work. 1. The Air Quality Indicator is useless. It stays blue (meaning good) even at readings that are clearly high on my 2 separate Air Quality meters. For example, with an AQI of 90 and PMI2.5 of 35 (both of which are definitely too high and cause problems for my asthma), the indicator on this unit still shows that the air quality is good. From reading other reviews, I think this is a design defect and not just a one-time faulty unit. 2. Because of the problem with the Air Quality indicator, that makes the Auto and ECO modes useless as well. If I turn on Auto, it just stays on low fan speed (which is very, very low) all the time. And on ECO mode it seems like it would just never turn on, although I didn't test that extensively. Apparently the air quality would have to be pretty severely bad for this unit to register that it's out of the "good" range. Whereas I need something to try to make the air quality as good as I can get it, not something where a moderately bad air quality is considered good. (There is a sensitivity setting for this indicator, and I had it set to the most sensitive setting. So the issue would be worse at the medium/ standard setting.) 3. The Fan speeds don't make any sense, meaning manual operation of the speed is also problematic. Speeds 1 and 2 are both quite low and don't do much. Speed 3 is then a very large amount of air moved and very loud. In other words, speed 2 is not in the middle between speed 1 and 3. It's much closer to speed 1, and then there's a big jump from 2 to 3. So I guess it would work if you wanted to manually leave it set to Speed 3 100% of the time. Otherwise, there is no speed that meets what I need much of the time, which is a middle speed. Again, after digging deep into other reviews and customer questions, I did see someone else reference this, so it's not just a one-time defect in the unit I received. 4. Other misc notes if you do decide to buy this - The Air Quality Indicator light is very, very large and bright, lighting up the dark room when I tried to sleep. Although the user manual doesn't mention this, you can hold the Ionizer button down for 3 seconds to turn off this obnoxious light. - Moving and unpacking the unit as shipped could be problematic for some people. The Coway box it ships in is fairly large and bulky, about 20x22x13, so quite a bit larger than the unit itself. So although it's not really heavy, if you have short arms and have to move this anywhere before unpacking, it might be a little difficult because of the bulk. It also means you have to be able to lift it almost 2 feet to get the unit out of the box (there's an inner box that is a very tight fix inside the outer box) or turn the box over. So again if you have short arms or have any strength limitation issues, the unpacking might be a bit of a problem for you even though it's not super heavy. Also note that the AC power cable has plastic tightly wrapped and taped around it, and there isn't any way to get it completely off without cutting. That could be dangerous if you accidentally cut a little bit into the AC cable while trying to get this off, so please be careful. It's also difficult to remove the plastic bag on one of the filters without cutting, so you do need a knife or scissors to unpack and set this up. Overall, I'm not happy with this at all and am going to buy something else. Update: I decided to give this one more chance. After trying it again, two further observations: - Even with an AQI (on my separate monitors) of close to 150, and PMI2.5 of around 50, the air quality indicator on the unit still shows "blue = good" on the most sensitive setting, so the auto mode still won't kick up being the lowest level - The unit has started making a whining noise, in addition to the normal fan noise. The whining noise, while not incredibly loud, is more obnoxious and annoying than the "white noise" of the fan, because it's more of a constant tone.