Well consider this post coming from a person that must be dead as I use a Mr Buddy. I use mine for extra heat when awake, I am not comfortable using when asleep. I love it!! If the camper is -20 I can power on the furnace and the Mr Buddy and have it up to 20C in 20 or 30 minutes. I use it to project heat to dry cloths. I use it when I am low on battery power as well as a emergency heat source should I need it.
I would love to have a vented cat heater but I just do not have the space.
Follow instructions and keep some windows / vents open.