I live in an 80-year-old six-unit apartment building, and the single-pipe steam radiator system doesn't work all that well.
I'd like to put in supplemental heating, and one good possibility seems to be a natural gas stove-heater.
I see that there are vented and unvented models. It seems to me that unvented might be a bit dangerous.
But I remember that years ago, many houses had room gas heaters with no venting at all. You just lit them, and the heat filled the room -- gas fumes and all -- and I don't remember any bad results.
Any guidance welcome.