Bests & Worsts Reviews from Amazon

Since I stopped using Hydro Cells in my Air-O-Swiss humidifier, there is one big difference I noticed: I have an extra $10 in my pocket every month. Other than that, nothing has changed--but that should be no surprise for these reasons: First, while activated charcoal can improve water quality, it can only do so if water is forced to flow through the charcoal. This is what happens in the charcoal filters of fish tanks, pet fountain systems, and even simple Brita water pitchers. It does NOT happen with the Hydro Cell, which simply floats in the tank with no flow of water through it. Also compare this to the demineralization cartridige: water MUST flow through the cartridge granules in order to leave the tank. Second, the benefits of activated charcoal are best realized in stiuations where water is going to sit or recirculate: again, fish tanks, pet fountains and Brita filters are examples. Typically, though, a humidifer's tank will be filled with fresh, clean water every day or two, so the need for charcoal filtering at all is highly questionable at best. Finally, even Air-O-Swiss can't tell you what the Hydro Cell really does or how it does it, beyond vague and empty marketing promises: it "ensures the highest water quality" and maintains your humdifier "operating at the highest level" and helps "keep the water fresh." Really? What do those claims even mean, and to what degree does the Hydro Cell do any of them? Also, how can it do them without water actively flowing through the charcoal? Air-O-Swiss has nothing to say. Still convinced you need the Hydro Cell? Try going wthout one for a few weeks and see what you think--you'll never go back to using them again. Thanks for taking the time to read my review and I hope you find it helpful in making a buying decision. UPDATE OCT 2015: In the manual for the U700 model, Air-O-Swiss goes into detail about how the Hydro Cell supposedly works: "The Hydro Cell activates as soon as it comes into contact with water. Its activated carbon technology filters helps reduce heavy metals, impurities, chemicals and remove pesticides from tap water. It also reduces odor emissions." Sure sounds great, right? But here's where the marketing-speak gets tricky: "activated carbon technology filters" actually CAN do the things that are being claimed here... but ONLY if you force the water to pass through the carbon filter. Fish tanks and pet fountains achieve this with a pump... Brita-type pitchers do it with simple gravity. The Hydro Cell does not do it at all.