Actually, CO doesn't feel like anything. You're lucid for the first several minutes, and then sleepy and dizzy a few seconds, and then you lose consciousness and die.

The trouble is that you'd have to seal the chamber the dying man was in, let the gas react out of the air for about 5 hours and then have an automated machine inside test the air occasionally to let you know when it was safe to go back in. Even relatively tiny amounts of carbon monoxide are very bad for you.

I have reason to know.