Here's another way to kill yourself. Propane DOES explode when 
mishandled. It's heavier than air, so when it leaks it often flows 
invisably to lower areasm where is concentrated until there's  
spark...then...BOOM! More energy than dynamite.

The heaters you mention (canon type) are designed for outside and highly 
ventilated areas like big garages. Then out out carbon monoxide and other 
products of combustion with their heat. Feeding that heat into a cloded 
van would be very dangerous.

Dave Garth