I don't know whether car exhaust is as effective as it used to be, but early one morning, I found a car behind a place of business, engine running, a double length of water hose (garden hose) with one of the ends inserted into the exhaust pipe and securely taped in place, the other ends into the back window of the car on the driver's side, also securely taped and sealed. And the owner was dead in the driver's seat. That was the only corpse I ever saw with a smile on its face. He left a note on the dash that said, "Life's too much so exit laughing." P.S. Don't tell (wife's name) until afternoon because she has an exam this morning."