Another Question About Humidity Control ...

I never heard that those have an effect on bank notes. Might or might not. I sure wouldn't want to find out by trying them and later saying shouldn't have. The problem I would think is pending on what country the notes or currency is from, may have all sorts of different inks used. This would mean that what works in one coutry, may do damage in others. A problem with any moisture absorbing item is once they get full, many people just let them lay there not knowing they no longer serve any purpose. And in some instances the excess moisture from them is emitted. If you get the rechargable ones or replentishable, might and might not work.
Again, rmember that bank notes from different countries may be of material that could be damaged by moisture absorbing substances.
IF you have a lot of them that are of little value, you may want to try using that stuff and report back to us of what happens.

As to the storage of currency, I have many of our US bills in plastic sleeves made for them. Then those are in Zip Lock Plastic bags. Been there for well over 20 to 30 years and no problems.