Product review (5 stars): Helpful in prolonging the life of the filter and keeping humidifier clean
After a great deal of research, decided to go with this product. I try to use natural cleaning materials and was very hesitant to introduce a new chemical to my home. But I realized that, even with weekly cleaning, my humidifier (Lasko 1128 Evaporative Recirculating Humidifier) would occasionally create a musty smell -- and that musty smell was some combination of bacteria and fungus. So I decided I would buy this.

This has been very effective in keeping the filter clean (the filter used to only go a week, and would be badly discolored at that point - it now easily goes 2+ weeks, and others report even longer life) and I haven't had any moments where there's a musty smell. The amount of product used is tiny -- a capful (perhaps 10 ml) per every gallon (3.8 liters). One note: it seems to be a chlorine based product, and it may stain clothes when it is in direct contact (before it is diluted).