Product review (5 stars): Reduced humidifier maintenance
These worked great in conjunction with the humidifier water treatment to prevent calcium buildup.  I would only need to chaneg these pads out about every 2 months and clean my humidifier once a week (2-gal filled daily).  The pads got hard indicating they were absorbing the calcium.  The remaining calcium would be airy/brittle versus compact on the heating element, probably due to the use of the treatment.