Running your propane Refrigerators while traveling?

MSchu wrote:
It says "especially in underground tunnels". Is that because propane sinks and would be trapped in the tunnel? would it be less of a risk in a mountain tunnel where one end is lower than the other?
I pulled my trailer through the tunnel in Zion NP where you have to have a permit to pass and they never even mentioned propane.

The word underground is misleading. Pretty much all tunnels are underground. Even the ones that go straight through a mountain from one side to the other are technically underground. So are the ones that go underwater. They are anchored in place with a layer of silt or sand over top of them. Whether they go straight through from one side of a mountain to another or down and then back up again like an underwater tunnel it really doesn't matter. Even if the tunnel has fans that are pulling the bad air out of the tunnel so fresh air can come in and there is an explosion there will be a fireball. That fire ball will travel in the direction the air is flowing in the tunnel.That is usually in the direction that the vehicles are traveling. This creates a blast furnace effect incinerating everything in the path of the fireball until it burns out. If the fireball is bad enough you can get a chain reaction of explosions as feul tanks from other vehicles cook off. Tunnel fires are not a very pretty sight. Even if it's just a car fire because of an engine problem or electrical problem there will be a lot of smoke created let the ventilation fans probably won't be able to keep up with.