Product review (2 stars): humidifier filter
This filter didn't seem to make any difference in the amount of white minerals emitted by the Venta humidifier.  It may have made a difference for a week or two at most.  I replaced the original one after 1 month and gave up on the second one after two weeks.  I returned the humidifier.  I don't know if breathing all the minerals is any better for you than the effects of dry air.