Product review (2 stars): How to get rid of the STINK
I bought a few of these, and they stink.

I came up with a way to make them not stink, though.  Set the humidifier outside.  Put a cup or so of 50-50 mix of vinegar and water in the humidifier.  Let it run until dry, and then pour in a cup or so of tap water and let that run through.

The smell should now be gone.  Vinegar drives out other odors and dissipates its own odor quickly.