I don't know the technology on the CO detector. Like "smoke" detectors, more than one technology is in use. CO detector is supposed to try to measure cumulative exposure as well as sudden high levels.
LPG detector is almost always a total organics device, usually looking for C-C and H-C bonds. There is a whole lot of stuff that will set those off, we aren't paying enough to get a device that will analyse the absorption spectrum to sort out one organic vapor from another.
Smoke detectors? Humidity will short out some types, that's why installation instructions say don't put it in the bathroom. A small RV closed up, when someone takes a shower the whole RV is a bathroom.