Lay people can’t seem to grasp how familiar, apparently innocuous gasses like O₂ oxygen, CO₂ carbon dioxide, H₂S hydrogen sulphide, CH₄ methane, O₃ ozone, N₂O nitrous oxide etc. become lethal if the global atmospheric concentration wanders out of a fairly narrow safe band either directly or through the greenhouse effect. CO₂ carbon dioxide (pop fizz) can kill you just as dead as HCN hydrogen cyanide (gas chamber).
~ Roedy (born: 1948-02-04 age: 64)