Currently this is the battery I am using for both starting and house battery application. This battery has the hose connections for venting to the outside. As out vehicles are used for habitation battery boxes should be sealed from the interior and vented outside. That is why the Westy has the battery box with the sealed cover and the hole to the wheel well. AGM batteries do also vent so using them does not make this issue go away.
This consideration is especially important if adding charging capability while being camped in such as a plug in charger or solar-wind etc.

Dennis

https://www.napaonline.com/en/p/NBP7541