i have an old vw camper van and i am looking at a portable gas heater to heat it up during the winter but i am worried that i may fall asleep with the heater on and die of carbon monoxide poisoning. I have been told to open all the windows but that would just make my van cold.

Burning LPG in a camper van is a recipe for disaster. Why not look into buying a cab night heater as used in trucks, I’m sure there must be a 12V version available somewhere or it might be possible to adapt the 24V version. Good luck, Gizz.