Product review (5 stars): these little things work great
I live in Texas & have COPD, my sinuses & even my lungs dry out so humidity is a must.  I am happy with these filters and they work reliably!  I is important to rinse these as they before each use.follow simple steps.  First if they get old and don't get rinsed, the top dries out & turns hard -If that happens, there will be no real humidity production.  The filter is designed to work when wet.  Also rinsing the filter is rinse harmful bacteria away, keeping it from being forced into the air you breathe.  (I sure don't want to purposely force something into the air I breathe that can me sicker!)  I just take the time to rinse each say I use it & those little things work great!