Of course CO2 is necessary for life. It would be ridiculous to argue otherwise. It's a matter of degree and balance however. It's hard to think of any substance

Of course CO2 is necessary for life. It would be ridiculous to argue otherwise. It's a matter of degree and balance however. It's hard to think of any substance more crucial for life than water. Yet, if you drink too much of it you die https://en.wikipedia.org/wiki/Water_intoxication#Notable_cases https://en.wikipedia.org/wiki/Water_intoxication#Notable_cas... Too much CO2 indoor is what we call poorly ventilated building.