Product review (4 stars): Extends the life of pricy filters, deodorizes the air and keeps it fresh too!
I use this in my whole-house humidifier to extend the life of the pricy filter it has.  It does a great job of keeping any foul odors at bay, and so far, my filter shows no signs of major wear.
The only improvement I would like to see, is the cap.  The label states to never let this chemical come into contact with your hands/skin, but its impossible to pour into the cap without the product dribbling down the side of the bottle and onto your fingers.
I wish it would come in a squirt top bottle to help with this issue.
I will continue to use this for the life of my humidifier!