Nasty old stuff the CO, during the early stages of poisoning, the victims supposedly go a bit daft and happy.
PhilipR
How true, expands your blood vessels and makes you look flushed and healthy.
Check out the WWII disaster in Italy, the Black Market Express. Labouring, overloaded train, burning low quality coal struggles through a tunnel. I think only a few guards who were in a van at the back survived. Possibly only one without health and mental damage. Hundreds dead. Guards reported that as they walked up the train to see why it wasn't moving, everyone looked fine and healthy, just dead!
My Aunt had a CO2 alarm that would go off all the time. My father arranged for a plumbing engineer to check for a problem. Eventually narrowed it down to the cooker, all hobs and oven fine, but when they tested the grill, it went off the scale. Replaced it quickly.
Mart.