Taking one huff to make your voice sound funny is fine.
Humans sense hypoxia from the buildup of CO2 rather than the shortage of oxygen. At NASA workers who wandered into areas purged of oxygen with nitrogen would not realize there was no oxygen and would continue until they dropped. Since they were still exhaling CO2 they had no idea they were suffocating. Huffing helium works the same way; you are still exhaling CO2 so you do not sense that you are not getting oxygen and you can literally continue until death without realizing anything is wrong.
Only danger is passing out, falling, and breaking something, especially your head.
When we were kids we played with a helium tank for an hour, singing songs as chipmunks, and by the end of it, we were all lightheaded and queasy, and nearly fainted a few times. Felt light headed for a few days afterwards too. Hopefully didn't do any damage though.
It actually is kinda dangerous. Is limits your oxygen going to your brain. I always do it when i get helium filled balloons, but my sister did it once & her eyes rolled to the back of her head & she just about fainted.
lol, its not harmful unless you inhail A LOT.... i think there was some thing on Dr. Oz show about it, you could look it up if that helps.
lol my advice ..... when you see the purple monkey stop for a bit till he goes away ;D
It isn't really dangerous as long as you don't do too much at one time.
Wow, that's interesting.