The answer to this question is theory
You could do a baking soda volcano or a diet pepsi and mento's volcano
The helium would expand into the air of the room. Depending on how big the room is, and the amount of helium in the jar, it could cause damage to health. The only way this would happen is if the room was small and the jar was big.
I hope this helps!
No! Acetone is a compound :)