Do not use damp rid. It has other stuff that puts out vapors.
Get silicone dessication form Granger or McMaster and keep in the bottom.
You are fine with open safe for a period of time but should keep it closed up as much as possible and the more humidity the more closed it should stay (I would only go in and out in Florida).
The Silicone get change color or the pack indicator will and when it starts to go from blue to pink replace it.