My grow room is in an area where noone but i travel to and where very little co2 gets to. I started the yeast and sugar water method for co2 a week ago, and so far, my plants have actually grown a quite a bit better in comparison to when i didnt have any co2 but my breath and what is in the ambient air. I dont believe that the amount that the yeast gives off is enough to kill me, but it does cover the smell of skunk quite well.
Back to the Point As jondog said, too much can kill you, and thats of anything(except THC
). Asphyxiation can occur as in Silos used for storage of sileage. Famers have passed out and even died because of lack of oxygen. In my EMT class we were told not enter silos, to rescue individuals, without SCBA masks because we could be overcome by the over abundance of CO2 in cellars where fruits are stored and by going into grain or sileage silos.
NASD: Silo Gases-The Hidden Danger has the explanation