I read a study that showed a properly functioning catylyic heater generates a small amount of CO, small enough that it didn't pose a health hazard but the oxygen level during the experiment went from 20.9% to 8.8% so death would still have occurred from hypoxia.
(link)Several years ago in Ontario there were a few deaths at a seasonal RV site when an enclosed porch was addedin a place where there was an exhaust vent inside it. Post incident investigation of the rest of the park resulted in finding a number of other trailers set up in a similar fashion (they were all evacuated and entry was prohibited until repaier were done)
