"Robert Laws" wrote in message
ups.com...


I have several dishes of calcium choride under the floor in my
narrowboat. it does keep it dry down there. But that it an
environment where new water vapour enters only slowly so only a small
amount of dehydration is needed.

I use it (in tubs) in the boiler of my steam roller. (over winter) It keeps
the RH close to zero and effectively stops the steel boiler rusting
internally. The crystals last almost 6 months because the boiler is just
about air tight, give or take some small leakage from gland packings etc.

Julian.