Product review (1 stars): Only made things worse.
We have the "Hello Kitty" humidifier and I bought this filter in the hopes of reducing the white dust from the humidifier, but all that ended up happening was that the water in the humidifier turned a dingy yellow-brown color and my daughter's room FILLED with white dust. We had to open the windows and turn on the attic fan just to clear it all out.  I'm not sure why this happened.  I followed the directions on the box (although it's 100% fool proof, all you have to do is place the filter in the base of the unit). We're actually better off without a filter and I'll be returning this for a refund.