Or a running vehicle with a hose on the exhaust, down the hole. CO build up.
“Or a running vehicle with a hose on the exhaust, down the hole. CO build up.”
Don’t know your age but I grew up with manual chokes on vehicles. Run a hose from the exhaust under a rat infested farm building floor and pull the choke on a bit. The CO content went way up because of incomplete combustion. Deadly stuff.