[dylan604]

>if the CO₂ is above 1500 I get drowsy, so the degree it is no longer responsible driving a car.

so the old adage of rolling down the window when driving might actually have some factual logic to it. of course, people are only considering that when at the extreme end of trying to stay awake from already driving past safe limits, but it could easily make a long haul trip more bearable by remembering to crack the window at intervals. then again, if you're riding with my buddies, you were already having to crack the windows at intervals, but for other reasons.

[Nition]

Also useful is having the fans set to fresh air rather than recirculate.