How much helium do you need to breathe in to hurt yourself?

what will happen to you? can you even hurt yourself?How much helium do you need to breathe in to hurt yourself?
The reason you feel 'dizzy' and lightheaded when you inhale large amounts of helium, is that due to oxygen deprevation. In layman's terms...the reason you feel like you are 'suffocating' is a buildup of carbon dioxide, which is released mainly when you breathe out. Helium is an inert gas, so your body can't really tell the difference between that and oxygen. Helium however, can't be used for body functions, and so your body has no oxygen!
You can easily die from it!
Its not a good idea to breathe in helium, I've done it before and passed out! if you do it, dont take in too much, and if you start to feel dizzy, stop straight away..
Helium is not in the least harmful, but an oxygen shortage obviously is. If you mix helium, 80% by volume, with oxygen, 20%, you can breathe this all day with no ill effects -- except for not being understood by someone you are trying to talk to.