Comment by outworlder

> If you inhale a lot of helium and pass out, your body doesn't start breathing again because there is no CO2, so you just suffocate instead of inhaling oxygen.

Other posters have pointed out that this is false(you will continue producing CO2 while unconscious just fine, chemoreceptors will notice). I would like to add that I have personally witnessed people falling unconscious from helium. They recovered just fine.

Really, the greatest danger is the fall.