Product review (4 stars): rinse before first use
These work great.  I didn't rinse these before inserting into my bionaire tower humidifier and within 20 minutes or so, my entire apartment started to reek of foul-smelling chemicals.  After thoroughly rinsing, the smell went away.  I did notice that these filters catch more minerals than the bionaire filters that came with the machine, so I will have to replace these more often.  Be careful about letting the water run dry in the tank; it seems to ruin these filters.