hey bonger, your theory is correct, but there is no way for you to regulate the amount of co2 your pumping into your room. most modern furnaces burn fairly clean, but i'm not so sure i would take the chance of offing myself like that. also keep in mind your also pumping a shit load of heat into the room. spend the money on a good co2 set up, much safer. also, make sure your room is sealed real good, and install a carbon monoxide detector somewhere around where you sleep. i use two seperate monitors just because i'm a little paranoid. :stoned: