What about dehumidifing? Is it better to do it inside the safe or at the basement level? If done in the safe, what is the best method?
If you have the safe on the main floor, you can usually bypass a dehumidifier, since your air conditioner removes much of the humidity.
If you safe is in the basement, I would recommend some kind of dehumidifier for the basement itself, as well as something for inside the safe as well. There are plently on the market, and the merchant who sells the safe probably has them for sale as well. Basement humidity is really rough on guns.