I have no idea how this slipped by me, but it did. We have used both Mr. Heater, and Mr. Heater Big Buddy heaters while boondocking in our motorhome, and love them. I ruined the Big
Buddy by running it off of a refillable 5 gal bottle without a Mr Heater in-line fuel filter installed, and ended up with two Mr Heaters to replace it. All have a built in low oxygen sensor, which will shut the thing down before you croak. But, not trusting to little gizmos like that, we never went to bed with them burning. The Big Buddy was our favorite, since it had a battery (four D cells) operated fan, which really helped to spread the heat around. It worked fine to heat the front end of our 32 ft motorhome, I have my doubts as to how effencient it would be in a home or appartment...