Well!!the biggest supply of co in an RV is the rigs engine. Can you or would you intentionally divert that in your RV? Second largest supply of the gas is that supply of electricity called a generator! Same question as before. Using a flue less heater likely the next. The last example will not likely cause you ill will if it gets enough oxygen (ventilation). Now you know how to see if it really does what the manufacturer says it should.
I know! That's not what you really wanted to know. There should be a test switch on the unit.
Now on to the next point!!! CO detectors are not propane detectors! They may double as smoke detectors, that will be stated in the literature.
For the most part propane will pour out any low level opening. Furthermore, stoichiometric ratio is hard to achieve, the fear porn in movies is for effect, and has little to do with reality. On a scale of probability I feel propane is on a scale of magnitude much less dangerous than a charging lithium battery.