>that's 0.2% CO2, it that CO2 is the result of respiration, it means that about 0.2% O2 was consumed,
replyI dont know anything about human respiration, but I know a little about chemistry and theres no reason to assume this is true. Basic stoichiometry.
According to a random article on the internet[1], nominal co2 production is 80% of oxygen consumption.
Your point appears broadly correct, just wanted to point out some faulty reasoning that could lead to incorrect results in the future.
[1] https://societymechanicalventilation.org/wp-content/uploads/...
CO2 concentration doesn't start at zero, and by coincidence, if CO2 production is 80% of oxygen consumption, consuming 0.2% oxygen results in 0.16% CO2, add it to the base 0.04% and you get 0.2%.
reply> O2 sensor in cars compare the O2 concentration between the outside air and exhaust gases, it needs outside air as a reference
replySource?
https://en.wikipedia.org/wiki/Oxygen_sensor#Automotive_appli...
replyIt looks that some O2 sensors that don't require a reference have been used (titania sensors) but even though they have some advantages, they are less precise and mostly obsolete.