The compartment that the on board propane tank is in is not completely enclosed. It is open on the bottom so it can vent to the outside world. It does have a manual shut off valve and an electrically operated shut off valve. They can be accessed after some work of removing the contents of the bay and unscrewing many screws holding a pannel in place. It is located between the frame rails of the Freightliner chassis. The access to it is the problem. That is why they tried to mount the external tank line for the Extend-A-Stay in a permanent manner. The hose was place on a hook in the main pass through storage compartment. The leaking check valve in that system leaked the entire contents of the 126lb propane tank into that compartment. Now, everything that was down there stinks of propane.
Keith