Product review (4 stars): Saves money on replacement filters
For several years we have used a large humidifier during the winter months.  Despite frequent cleaning and care, we had to replace the humidifier filters every few weeks.  We started using the Holmes Bacteriostat last winter and only had to replace the filter a single time, three-quarters of the way through the winter.

Follow the directions on the bottle and not only save money by not having to replace the humidifier filters as often, but it can also save you from breathing mold spores growing on an untreated filter (before the filter even looks like it needs changing).