Over many years and different vans, the majority VW, I've often used my
cook stove for quick heat.  I've believed that my vans "leaked" enough
outside air that asphyxiation wasn't going to happen.  This is probably
wrong, at least in my tin top camper.  Just now, it being around freezing
in the pre-dawn desert SW, I brewed coffee and left both westie stove
burners on high for some heat as I watched the sunrise ....  I saw my
burner's flame diminish and get thready.  Thought I was out of propane...
But I discovered that a kitchen match, the "strike and light anywhere"
kind, that would not light!  No O2 or too much  co2....whatever, pretty
scary.  I ran back the slider and let some air in, things burn normal again.

So I believe the warning against using the cook top for cabin heat.,..now.
I just saw why.