Product review (5 stars): Recommended!
This product is GREAT! i have 3 humidifiers and I use regular hard water, this solution prevent the development of scummy mold from forming.  For all who posted a bad reviews due to chemicals, I use a cap full per 1 gallon of water and I absolutely have no issues as the solution is diluted with water.

PS. I am using it with ultrasonic humidifier for the past 3 weeks and its working great!