Lots of good info. on venting sealed battery boxes on the internet such as:
hydrogen ventinghydrogen ventingBD BatteriesI found a great website not too long ago but can't find it right now.
The exterior vent should be min. 6" above the top of the battery box. Not sure if temp. inversion can be an issue in an RV but FWs use the MTS products sealed box and come that way from the factory.
FW sealed boxes I don't know if the inlet location into the box is all that important but you don't want it going into an enclosed underbelly or inside your camper in case the gas flows in the opposite direction. Small droplets of acid can apparently escape the outlet vent and you don't want it near anything metallic.
Those common MTS Products sealed battery boxes are a PITA because the halves are held together with bolts/nuts which makes it hard to check the water level or remove for winterization. There are some other boxes that don't use bolts/screws. I used the MTS one once and never again.
If I install a battery inside again, I'd use an AGM type in a sealed box in case it ever off-gases.