LP lines inside?
The video states that the propane tank tank and glass mat batteries are also enclosed, which does not necessarily mean they are inside the cabin space, or sealed up in a non-ventilated compartment. This is a common feature with many 5th Wheel RVs, and some travel trailers. Even though ours are enclosed, the cylinder storage area is open on the bottom and lower sides of the enclosure. The cylinders are well ventilated and I suspect the same can can said for the cylinder covers Airstream uses on some of their rigs.
My lead acid batteries are mounted in the front bay and vent to the outside via a flexible duct.
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