And place it low. If you've any propane connections or valves inside the van then you should have one. CO will kill you quietly, propane has a more vigorous way of expressing itself. The one in our van is not battery powered; it's wired to the 12V coach battery. I take out the fuse to keep it from running down the aux battery. When the propane is on, the fuse is in.
While we are being van geeks, I have to brag about a new bike rack I designed and had made. We wanted to have an easy, and safe, way of mounting our bikes inside the van. So I designed a bike rack using parts from a Thule rack and a manufactured piece that fits into the floor track of the removable back seat. Called a local welder, faxed him some plans, he welded it up, I primed and painted it. Tested it out this weekend and it worked really well. I can get the bikes in or out of the van in under four minutes and they barely wobbled during the 30 mile drive. And we can still get into the 'fridge when the bikes are in there. That's really important.
Patent Pending ...