We had analyzers to test the storage atmosphere in these room after they were filled with bins of apples and sealed with doors that were bolted shut.
The before atmosphere in the rooms, that is the same air that we breathe, contained .04 percent carbon dioxide.
After the atmosphere was removed and the room was considered in CA (controlled atmosphere) the oxygen level would be held at 1.5% to 2%. The CO2 level was kept to near 0%.
The object of the procedure was to put the apples to sleep, but not kill them, that is make them decay or to have a grape smell and taste.
CO2 is the by-product of the ripening process.
This is a synopsis, although brief, but gives a value to the amount of CO2 that is actually in the air we breathe. Also, the air we breathe is roughly 21% Oxygen and 78% Nitrogen. The remaining 1% contains the CO2 mentioned above.
The remaining 1% consists chiefly of the noble gas Argon - and a tiny portion of carbon dioxide (about 400 ppm).
Regards,