I just drink oxygenated water and my farts smell fine…

Yes. There are special controllers to manage the air going in and out as well as the Co2 dossage, it is essential to use proper controllers with Co2, it is toxic to humans at a lower levels than it is to plants and it cost enough to not want to waste it.

I run CO2 I cycle my intake and exhaust fan 1 minute on 15 off. My CO2 is 1000 ppm I barely go through it that way. And the timer shuts it off at night.

I grow in sealed systems with no air exchange. I supplement CO2, the plants produce the O2.