Officials in California will hold a news conference later today to talk about Robin Williams suicide Monday. They did say the cause of death was "Death by Asphyxia". Quite literally, that means suffocation. Princeton University says there are different way to die from asphyxia.
One way might be to enter a tank with a low level of oxygen. You would pass out rather quickly.
You could breath gases like helium or nitrogen.
But the simplest way to do it is to go into a closed car in a garage and turn the car on. Or you could get into the car and run a hose from the exhaust.
We should know more after to autopsy today and the news conference.