If you are in a car and the car turns a corner, the balloon goes to the INSIDE of the curve. That means if the car goes right the balloon goes right, but you lean left. That is because the heavier air goes to the outside and the lighter helium floats on air. Even if the balloon is intact it will still go flat. Helium atoms are so small they will go between the molecules of most containers. Balloons are made of aluminized mylar because that combination leaks the least. BTW the same is true of oxygen and zipper storage bags. That's why they are made in three weights. Sandwich bags only need to hold up for one day so they are thin. Storage bags are thicker, and freezer bags are thickest to keep oxygen out for weeks or months.