It is not possible to survive by replacing oxygen with helium. The body cannot use helium for cellular respiration and would very quickly suffocate. The chemical processes involved in cellular respiration would not work with helium, so there is no way to adapt your body to do this.
The air you breathe out is denser.
It depends on what you mean. We can breathe helium without any ill effects as long as we get enough oxygen. However, nothing could breathe and use helium as we breathe and use oxygen because helium is inert. Unlike oxygen, which is highly reactive, helium does not participate in chemical reactions, so it could not serve an organism any purpose.
they can breathe it in
helium is less dense than the normal air we breathe, so when you breathe helium out and your vocal chords vibrate, it comes out in a higher pitch tone.
you will talk squeaky
Helium itself is completely non-toxic. It is only dangerous if you breathe pure helium without a supply of oxygen.
Helium is used instead of hydrogen because it is nonflammable.
Helium doesn't cause cancer, so from that perspective it doesn't matter.
No. It is an inert gas. But, if you only breathe helium, you may deprive your brain of oxygen, and that can be fatal.
Not exactly. Helium is an inert gas, and is not toxic.However, you could die from not having oxygen, so if you breathe only helium, yes you could die.
if its possible then the reason could be the expansion of high pressured helium from tank to balloon is large.
No however the lack of oxygen is deadly. It is unlikely that you will hurt yourself sucking the helium out of balloons, as long as you breathe oxygen in between breaths of helium. There is a small percentage of helium (.0005%) in the earths atmosphere.