Product review (5 stars): Wish i knew about this earlier!
I bought this because i use my humidifier daily and my room started feeling muggy and smelly. Not only did the smell go away after using this, i no longer had to deal with the dirt and  gunk in my humidifier. The one i have does not have a filter and i was thinking of returning it because of the residue which slowly decreased the quality and amount of mist. However, once i starting putting a cap and half full of this liquid (I have a 1.5 gallon tank) all my issues disappeared.
I think this is definitely a great buy and wish i knew about it before my walls got streaked with residue.