Product review (5 stars): Not a trace of mildew or mold in our humidifier
I have a pretty good sized humidifier and I have a small portable one that takes .5 liter water bottles.  The big one that runs constantly and gets this bacteria preventer has never shown a sign of mold or mildew using tap water.  The tiny humidifier, using bottled water, gets slime and mold if I don't clean it every few days.  I'm just not sure how to safely dispense this product in such smaller quantities - perhaps an eye dropper - or I would use it in that humidifier, too.