I have had this unit since early November 2011. As of mid February 2012 I have to say it really is not perfectly clear that this is working but I don't sneeze as much in our bedroom. I bought the unit because I got very ill and was hospitalized with a chest infection that I believe came from mould. I do believe it's working but it is very hard to give a solid level of how well it works and what it does. It's small and quiet. It does put out a bit of light, even though this unit does not have the blue night light on top, so if you don't like that then it will bother you in a room where you sleep. I intend to unplug the unit and see if there is a change in my breathing and will edit when I do.