At 03:24 PM 2/4/2009, Larry Chase wrote...
>To quote from the Mr Heater Manual;
>
>"This is an unvented gas-fired portable heater. It uses air (oxygen)
>from the area in which it is used. Adequate combustion and ventilation
>air must be provided."

Why stop there, except to mislead? It goes on to say:
"This heater requires a vent area of 9 square inches (example 3" x 3"
opening) minimum for adequate ventilation during operation"

That's not much of a requirement. I suspect (but won't claim it as
fact), that most Vanagons are less tightly sealed than that, and that a
normal Westy canvas breathes at least the equivalent to that. If there
are any doubts, one doesn't have to open a vent or tent window very
much to get 9 square inches. The O2 sensor/shutoff is just a backup to
that very minimal requirement.