So, I've mentioned that I plan to build a super insulated house when I settle down. I am constantly refining and changing things to try and make it as energy efficient and comfortable as possible without losing all the creature comforts but also without making it way too much work that someone needs to stay home 24/7.

Most likely ICF construction for the bottom and top. Currently looking at a half buried basement, all the living quarters downstairs, with the working areas in the "main" floor.

My question is this,

Can I use a rocket mass heater in the "basement" or am I risking mass exposure to carbon monoxide?

These are rare enough I don't expect anyone to be an expert and I have done tons of searching but it hasn't helped. My concern is that since carbon monoxide is a heavy gas and the ICF is so vapor tight that it would be dangerous. I have never really seen a fireplace in a basement, just a furnace and they were never a living space in those kind. This will be used as my main source of heating, with a regular stove tied into the flue on the floor above.