Product review (5 stars): saved my little vaporizer!
I have one of those cheapo vaporizers from the drugstore, which worked great the first few years, and then started having problems.  I have faithfully followed the cleaning instructions (vinegar, then chlorine), but it was obviously building up too many mineral deposits.  I tried CLR (calcium lime rust) remover, but that was only a partial success.

I just put a little bit of this into the water every time I fill it, and the mineral deposits flake off the heating device every time.  Also, when I rinse out the plastic basin, it always looks clean now, instead of covered in [whatever minerals they are].

I only use a little bit each time, so I never worry about inhaling excess chemicals.  This is a great product!