Product review (4 stars): Keeps the "slime" away
I use ultrasonic humidifiers and lots of problems with white dust emissions and bacteria buildup and sometimes a "slime" getting deposited on things including my skin and hair! So while I treat my nasal allergies and blockages and breathing problems, I'm irritating my skin and scalp with all these deposits. I have tried every type of humidifier and always go back to Pure Guardian with a built-in silver filter. They produce a lot of white dust but using this treatment keeps the water sanitary so i get a lot less funky stuff on my skin. I use actually 3 caps in each tankful which is probably 3 times what they recommend, but we have a lot of dust and pet hair in our home being constantly filtered.

I also use the extra filter now for less dust that screws on to the cap of the water tank of the pure guardian which definitely reduces dust at least somewhat. And I always, always use this water treatment to keep the steam from getting "slimy".  I don't mind dust nearly as much as that bacteria-ridden slime. And I find this to seem to be gentle enough to use in the Pure Guardian tank. It's also a huge help in other types of humidifiers that build up a lot of bacteria, and better for the machines than bleach.