Unfortunately we purchased the six filter package and have recently tried two new filters and they are putting off a bad smell when being used.  We did not have this problem with the filter we used with our humidifier when it was new.  I think I finally may have located a store who carries them, so I will try to purchase one more in the hopes that the filters are just old or something.  Very disappointing.  You may wish to purchase just one filter and not the six pack so you do not have six bad filters like we received.  You can run the humidifier without a filter if you use distilled water.