Old thread I know. This is actually a very personable topic, at least for us. We had a close friend die of carbon monoxide poisoning. All 3 fail safe's failed IMHO. Every one of them was working properly according to the fire marshal's investigation though ....figure that one out.
So, we have been using our Honda eu2000i generator, at almost idle, to run our Patton PUH4842M-RM electric heater. It works great. Zero fumes, zero carbon monoxide. Generator is placed well away from tent or camper and locked to something substantial, just to keep honest people honest. It has an over heat shutdown and a tip over shutdown. It also has a thermostat. It works fantastic and has been for over 10 years. We liked it so much we bought a 2nd one to keep in our 18' high ground clearance camper. On low, it is enough to drive you out of the camper unless you have the thermostat turned way down. Inside the tent, I usually set it on a cement block or bungee it to one of my stacking Ridgid tool boxes, to avoid tip over in the middle of the night. Generator will idle for 8 hrs or so when it is on low.
I see other types of fuel heaters can sometimes be finicky or need parts periodically. Sometimes when you need them most. I know many have done things differently for years with zero issues but us personally, we just won't take that chance.
Only things I have done to the electric heater is : drill a hole through the back plastic panel, in the center of the fan, so I can put a few drops of electric motor oil onto the backside of motor shaft & then cover hole with a piece of electrical tape, & blow all the dust out of intake and heater coils, every year.
They get used too. One does double duty in our back hallway of our house. We have a unheated back hallway with a half bath. No basement either. Just an unheated crawlspace. Pipes are wrapped in lots of insulation but the electric heater keeps the pipes from freezing where is comes through by the wall.
YMMV