I don't know if it's a viable option, but over on the Classic Campstoves Forum there are frequent threads on old campstoves --Coleman, Primus, Optimus, etc.-- causing CO deaths when used in a tent. Kerosene is not so clean burning as propane.
And my father-in-law ctb by closing himself up in the family car with a barbecue. Big car, too: an old Dodge Ram Charger.
A "well duh!" observation: I suspect that if the appliance isn't intended to be used in an enclosed space, it may lack the CO safeties and thus is probably a lot better for ctb in an enclosed space.