Safes are just a way of delaying the heat from reaching the contents in case of a fire. If you leave any safe in a fire long enough, the contents will be the same temperature as the buring material outside. You just have to remember that your house won't burn forever [g].

A safe intended to protect paper will do a good job to protect chips for most structure fires. If you want to double up, you can put a small fire safe or insulated document box inside the steel safe and buy yourself some more time.