I had heard several years ago that emissions on a new car(no year given) were so harmless that if the vehicle were run in an enclosed area that the vehicle emissions were relatively harmless. Is there any truth to this?
Once the catalytic converter warms up most of the CO in new cars is converted to harmless CO2 and water vapor. But when the car is cold even new cars are still producing CO.
I once went on a call where our naked “patient” ran out of his house and into his garage and started up a lawn mower. The police had just arrived because he started out by pulling out a gun hidden in his couch and trying to shoot me.
The police sergeant asked if the lawn mower exhaust would kill him. I correctly predicted that he would give himself up long before losing consciousness. But your typical lawn mower probably produces more CO than most newer cars because of incomplete combustion and no catalytic converter.