My camper's battery box had a 2 inch hole in the bottom for ventilation.
I also assume if it burst and the acid leaked out it would be better for everyone if it was "outside" on the ground (where rain water would dilute it) rather than eating away the frame of the camper waiting to be discovered by a bare hand wondering what all the liquid was.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW