Product review (5 stars): keeps the creepy-crawlies out of your air
This stuff works well. We have two humidifiers going almost constantly during the winter, and even though we scrub the humidifiers  clean about every 4 days, without this stuff, mold grows on the filters pretty fast- with it, we get about 3 weeks to a month for a filter. Not bad. And the air doesn't smell bad either.