Sean, One of the things that I discovered in my checkout of my refrige is
that the little tube that comes out of the bottom left (near the floor) is
a 'combustion chamber' drain tube and this should have a cap screwed into
it to seal it.  I suspect that if it were missing, then opening a window
while cruising down the road could indeed blow out your flame.  The
combustion chamber is connected by two tubes to the outside vent on the
side, so in theory, it should not matter what you have open or closed in
the van.

John Graham
88 Westy
Charlotte NC