I'm not sure what "kept turning over" means?
Is the burner turning on?
CO2 is a byproduct of the flame, but unless the exhaust venting is missing or blocked you wouldn't have a CO2 build up in the house. CO (carbon monoxide) would be the bigger concern, but on an atmospheric-drafted beast like a Burnham CO2 exhaust leaking into the house isn't usually an issue unless you have an extremely tight house and you have the clothes dryer or other high-volume exhaust vent running causing the flue to run backward. (not likely.)