As both a long (6mos.) and short (<5day) term occupant of a bus in winter 
periods I have NEVER EVER left any form of combustion heater running for 
more than the 10 minutes required to take the chill off the inside, AND ONLY 
when wide awake. I expect to sit round in a down vest etc, with booties on. 
I don't expect to live like  I do at home. Think how much better off you are 
than being in a tent!!! Cook your breakfast or whatever dressed and sitting 
up, that's the only safe use of a stove. Don't try to warm the van while in 
bed, unless your system is on a (working!) timer, like the gasheaters. If it 
gets warm I gets sleepy, and that's a good way to die, whether it's from CO 
poisoning or O2 depletion who cares.
 The only heater I 'trust' is a thermostatically controlled electric fan 
heater, all others can be "dial a death" systems. Garths note was not 
trivial, CO kills really well, remember that for when you want to suicide 
out. Buy a good sleeping bag! If you're going for "warm and toasty all 
night" with a non-electric heater please put me in your will as next owner 
of your bus. TIA.    tim s.