Kaboom knew what they were doing with this product. It &******* perfect for tough stains.  Yes, the smell is a little potent so if you are sensitive to that and/or don't have sufficient air circulation available it is definitely something to be conscience of. I personally think the fumes take a back seat to the cleaning power of this stuff though. Flip on the fan and wear a mask and you are ready for some super cleaning power. It really just dissolves mineral deposits like nothing so I would really recommend it for that.