What's the best way to store an important document in a fire/water resistant chest?

I just purchased the SentrySafe CHW30220 Water-proof Fire-Resistant Chest for the purpose of keeping my important documents safe (like birth certificate, passport, etc.). However, I’ve read that these types of chests/safes are prone to high moisture (which kinda defeats the purpose of keeping paper documents inside IMO). So, I also bought some silica gel desiccants to keep inside. I also have the documents in acid free sheet protectors. Are those enough to keep my documents from getting ruined by moisture? What is your experience with keeping important documents in one of these safes?