I'm not sure that the fumes of non-aerosol sulfuric acid are worse than for average bathroom cleaners, and I wear goggles and gloves to prevent burns. I read Health Effects of Sulfuric Acid
. But I also heard about a guy and his family who passed out from using a commercial drain opener in their home so I have a strong fan aimed in the bathroom and I keep the windows open. Unfortunately, the exhaust fan for the bathroom isn't working for me and about 100 other tennents. The super is waiting for a motor. The building inspectors should check the fan because nobody but me seems to notice when it stops.
I always see the big CLR bottles but all I knew was that acid worked. I'll try the CLR when I run out of the Acidic Toilet Bowl Cleaner (which is also a Zep commercial product).