Not sure how long CO takes to hit you but it’s cousin CO2 hits ya FAST! Back years ago I was a beer rep, I was at a restaurant and went to check the kegs, opened up the cooler door and it smelled funny, natural reaction was to do a couple quick sniffs.... their was a keg line leaking (smell was the beer or other kitchen mistery smell I’d bet as I assume pure co2 doesn’t have an odor though idk that for sure). By that second sniff, I was lightheaded as cud be instantly and stumbled backwards to push door open... had to hold the wall a minute or two and then was fine but I’d venture to say one more sniff and I wudda been a pile on the ground.. don’t screw with it O2 is a handy thing to have in your bloodstream... any real experiment could be deadly- you walk in and pass out 10 steps in and you are toast...