Well, On the CO2 topic... You have to take into consideration that Commerical Hatchries take CO2 into consideration because their incubators are jam packed stuffed to the brim with eggs. As those eggs hatch, the chicks are using up more air inside than the incubator can hold. The hatchery that I lived next to when I grew up, used Co2 levels to determine how far along the hatch cycle was. Once the Co2 levels were at a point, they would pull the trays and off to the next part of the hatchery they would go. Im glad I never got to see that part. That was the sexing/culling room. As a 10-14 year old, I would have been devistated.
our incubators don't have that problem, unless you are jamming 80 hen eggs in a 1588..