Not very effective
Tried this on my Vick's warm mist evaporative humidifiers.  Descale them once a week after 24/7 running so they are pretty caked up.  This stuff did nothing.  I normally use CLR and let it sit for 10-15 min, then scrape the buildup with a plastic spatuala.  Maybe this is for daily use and my humidifiers were caked up.  I will be going back to CLR which I immediately see foaming and the flakes of minerals float off the humidifier heating element.
Rating: 2 stars