"But assuming it was a treasure hunting expedition (and the lower floors of the tower were reasonably cleared, with a path of escape blocked only by wandering monster rolls) what would a party need to do in one of your games to safely open a chest?"
Here are 10 ways to open a chest safely!
10. Pour acid in the lock.
9. Use a pick and chisel to break apart the lock mechanism.
8. Use a crowbar and specialized tools to pry the lock out of the chest.
6. Carry the chest back to town and pay the thieves guild to open it.
3. Unscrew the lid hinges.
2. Pry off the back of the lid!
And the number one way to open a chest safely?
1. Have the thief open it, there's always more where they came from!
Why don't they just do these things by default? They are time consuming, loud, or require heavy encumbrance penalties.