I have a natural gas heater and a natural gas range, both of which could be converted to propane. Why is the carbon monoxide so dangerous with a banjo burner, but not with the heater or range? I've looked around but can't seem to find a definitive answer. There do seem to be a lot of people using camp stoves and other lp stoves indoors without incident. What I can't tell is if they are simply really lucky... I am not referring to any danger from the location of the flame, boil overs or leaky gas lines, etc, purely with respect to the ventilation requirements and carbon monoxide.
I don't think the danger is in the output of CO. CO will pool on the ground rather than up to your face where you breathe. I think the larger danger is with propane/fuel leakage, which will also pool on the floor... right where you won't be able to quickly register the odor marker and right where the source of ignition will be.
Say you had a leak at the valve that pushed volumes of propane back into a corner, while the bulk of the propane was being delivered to the burner... wait for that area behind the burner to reach a critical volume where that gas is going to push toward the flame and then... get ready to call the roofers!
I did some more trolling and found this. In the first paragraph; "Properly functioning propane appliances will produce what is called an "ideal burn" during combustion and present no danger of Carbon Monoxide poisoning." The article goes on to indicate the ideal burn is a blue flame. A lean or rich burn however, produces unsafe levels of CO. There are other dangers, but specifically the danger of CO poisoning and why this danger isn't present in a gas stove or heater was the point of the question.