Jamie writes:

Sorry, my mistake. But regardless, CO can kill you very quickly...
even from a car, with a catalytic converter, and certainly from a
generator which probably doesn't have one.

Yes, a 1-cylinder B&S/Tecumseh/Kohler/etc is typically far worse than a
modern auto engine as regards emissions.

The risk should never be understated.

I disagree. That philosophy leads to those user manuals that start with 10
pages of warnings that nobody reads. Rear-view mirrors that warn you about
things appearing smaller. Caution should be proportioned to risk. Cf the
boy who cried wolf. Probability, hazards, and risks are about the hardest
intellectual concepts going; we ought not to be burdening people with any
more than they need.