CO2 does displace Oxygen though fellas, Once your passed out there aint no coming back......
True, Co2 will push out air.
I know for a fact that my propane heater comes with a ODS, for the pilot, I assume that high levels of co2 will cause the pilots in both my co2 burner and heater to blow out because they will not be able to support combustion for the pilot, shutting down any co2 production.
Now I have a 3 gas alarm for the space, but it does not cover low o2 or elevated c02.
Co2 is best for unoccupied spaces IMHO.. I prefer more ventilation in spaces where people and plants are growing.