Product review (5 stars): A welcome alternative to tank inserts.
This solution is for cool mist evaporative humidifiers *not* the ultrasonic kind. If your humidifier has a wicking filter, this will work fine.
Since I run a humidifier in the winter months to improve respiratory comfort, I didn't think breeding mildew and bacteria was the best idea.
There are tanks inserts which are available, but they only last for 30 days, which becomes cost prohibitive by the end of the season. One capful of additive with each new tank full of water and I no longer had to replace the wicking filter on a regualr basis. I have enough left from last winter to get me through the next season if not longer,