Re: Put a heater in the safe then ?
Most contemporary safes have a 3/8 inch hole drilled into the lower right rear to pass a power cord through. My Heritage safe (6' x 3' x 2' interior) uses a 3 watt heater, and I've never had any condensation problems, even with a damp basement. The hole equalizes air pressure so you can open the door after barometric changes, too.
