If you have a gun safe, especially in an area that is not regulated by your heating and air system, you should invest in a simple dehumidifier to protect your investment. Dehufmidifiers keep the temperature inside your safe to a constant level with no more energy than that of a small light bulb. By doing so they will keep condensation from happening on your firearms, which as we know can cause terrible damage.
Most safes will have a knockout in the back, or a pre-drilled hole that only requires drilling through the fire-retardant material for installation. Once you have installed the dehumidifier you simply plug it up, and you are finished.
I have been using the GoldenRod dehumidifiers for several years with no complaints. They retail for about $20 so it isn’t a costly protection for what you get out of it.
To properly store your guns, give them a light film of oil from a cloth and store them out of cloth cases in the safe. This will keep moisture from accumulating on your guns and should provide a rust free environment for storage.