Yes you are right, I was thinking of carbon monoxide not dioxide as yourself and others pointed out.

Why the hell don’t we just swap their air supply with nitrogen? No medical knowledge needed, no pharmacy needed. Considering the number of engineers in the defense industry they don’t exactly have a Hippocratic oath. Most of air is nitrogen so your body doesn’t fight it. You just feel stupid and loopy and high like losing cabin pressure in a airplane. CO2 or Helium would work as well.