Dehumidifier

That would be a good idea if you have a large amount of coins. Another god idea is to keep an open bucket of rice in the closet where your coins are. Silica also helps to absorb moisture

So much depends on where you live. Buy that I don't mean Hawaii or Arizona, but in a house, apartment, condo, etc. And how you live too. Regardless of anything, if you live in an area of high humidity and have all the doors and/or windows open a lot, a dehumifier is sort of a waste. You would be attempting to dehumidify the World. If in a house and there is a basement, those places accumulate Humidity due to it's weight in the air makes it go to the lowest areas of your home. People in apartments or condos are at the mercy of neighbors. Lots of cooking creates fumes of all sorts of gassses that can seap from one place to another. Living in any place where people have pools and those are treated with Chlorine too can play havoc with coins.
I use a dehumidier in my house. It is in the basement with a hose from the bucket to a drain. During parts of the year it is on so much I worry it will just wear out soon. The amount of water it collects is massive. A long time ago I heard so many stories about Silica jells that I tried a pile of them in the basement. I shut off the dehumidifier to see how well they worked. Using a hygrometer I found the humidity in the basement went up to 40% to 50% in a few days with those. I turned the dehumidifier back on and it dropped to 20% but took two days. Those gel packs are OK but most people forget they only hold so much moisture and then nothing. Must me monitored and either replaced or recharged. A dehumidifier like mine just sits there and works.

Go to the shoe dep and try on shoes, while at the same time accumulating all of the little packets you can...


Oops did I just say that

Silica gel and dehumidifiers are great, but they are pretty much worthless UNLESS the coins are in a sealed environment. If they aren't as soon as you remove the humidity the air dry exchanges out of the area and is replaced with more humid air. A dehumidifier will lower the humidity, but it will have to run CONSTANTLY and as soon as it stops the humidity will start going back up because rooms are not sealed. If want silica gel to work keep the coins stored in ziplock bags with packets of silica inside. For even better protection double bag with silica gel inside both bags. The gel will remove the moisture from the air inside the bags, and the bags, while not completely sealed will greatly reduce the transfer of humid air from the outside to the inside.

When you access the coins you should replace the silica with freshly recharged silica when you close them back up again.