Room for Improvement
This is my second unit so the three-star rating has to be taken in that context.  The first unit was sent to a clinic in a third world country.  It was greatly appreciated so I bought another one for the clinic but decided to test it before shipping.  My sense is that it does, in fact, do a rather good job of cleaning the air and it works considerably faster than expected.  However, and this is unfortunately quite important, it does emit ozone.  It seems to improve the air quality up to a point and then the ozone is quite unbearable and probably not particularly safe either.  It does not seem to have any on/off switch nor settings so the only way I see to stop it is to unplug it.  This is not difficult, but it is a tad inefficient and awkward.<br /><br />For its price and tiny footprint, it does a remarkable job, but there is significant room for improvement.  That is the reason for knocking off two stars, but even if features were added, the ozone would still justify some reduction in praise.  If one were not going to use the unit on a continuous basis, this type of air purifier would have a place in any situation in which odor or germs were occasionally introduced.  However, for continuous use, I think a higher quality and perhaps more expensive purifier would be better.  The unit is not silent at all.  It actually makes quite a bit of noise, enough to prevent me from sleeping.
Rating: 3 stars