Options
If you store SLABBED coins in a fireproof box....IN A SAFE....

is it best to latch the lid on the box down or leave some ventilation?
Speaking of effect on coin surfaces and NOT fire safety. Assuming you don't store sulfur in the safe also but also have guns in there?
0
Comments
If the safe is closed, it is all stale air. What would be the point of ventilating? Moisture?
That's why I ax...er... ASK.
Oh wait. The safe should be ....CLOSED ??????
Do you expect a net ingress or egress of sulfur and/or humidity? Usually closed is the right answer.
Aercus Numismatics - Certified coins for sale
I've kept my safe closed with a couple of boxes of desiccant. Many years storing slabs with no problems, but I would not store paper collectibles there, not where I live (humid), even with the desiccant. Guns, no idea,