Bought this recently, can't comment on efficiency and efficacy of unit BUT 2 things:
1 - the plastic unit should have moulded grips built into it so that you have a fighting chance of lifting it without having to tilt and grip from the very bottom - this is frustrating and a design hazard - i.e. its a good way to pull your back
2- The user manual is a joke. Small, poorly executed, Drawings instead of pictures. Minimal descriptions. It needs to be a larger size with crystal clear large photos to help setup easily, and everything in the box should be explained well. i.e. The unit comes with two pre-filters of different colors. I had to scratch my head for 15 minutes to figure out if I should use both pre-filters or only 1. AND What is the significance of the two different colors? Does one preform better than the other in certain circumstances? Apparently not. Then why have two different colors - just to perplex your buyers?????