Product review (5 stars): Semi-active humidifier works as long as your heat fan blows
And that's exactly when you need extra humidity the most.  So the concept is sound.  And it works efficiently too.  My nose feels less dry and as other said, it cannot fail.  It's a lil' labor intensive as you need to replenish it almost once every 2 days in my case.  But somehow I just ordered another one of this while my fancy Air-O-Swiss is still collecting dust (& calcification).  That tells you something, doesn't it?  This is to Air-O-Swiss like the Aeropress is to an espresso machine. Also, humid air holds heat better which translates into energy saving by setting your thermostat lower during winter months.  The difference is very obvious.