Product review (5 stars): If You Use a Humidifier, You HAVE to Buy This
A game changer for humidifier use.

We used a humidifier during most of the winter because of forced hot air heating. Before we had used this it didn't take long for a filter to get musty and gross.

With a cap full of this stuff at each fill up the filter lasted an entire winter without ever getting musty...even towards the end of the season when it's use is intermittent.

The bottle is large and should last for multiple season.

This is a no brainier, but this.