I just saw where Walmart has a balloon kit that comes with a 9 cu ft tank of helium, that could be a lot of helium.
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The only "spec" on balloon grade helium is "it will float a balloon."
While most commercial offerings are at least not toxic at surface pressures (and many add oxygen to keep it from being fatal should some kid breathe too much of it at a party) there is definitely *no* assurance it is safe for breathing under diving pressures. Just don't try it.
Rick
You cannot die from breathing too much helium or any other inert gas at 1 atm unless you fix it so that you continue breathing it when you are unconcious. In order for it to kill you, you would have to continue breathing it for several minutes after you passed out. If oxygen is added, it is to prevent from being used in suicides.
After seeing several helium filled baloons sink prematurely, I would, definitely conclude that there is more in the mix than just helium.
This is a false statement - there are more than a few accidental deaths to prove it. If any gas not containing oxygen is breathed long enough it will kill you. The problem is that since the human breathing response is mostly tied to CO2 levels and not O2 levels it is quite easy to breathe an inert gas long enough to deplete the oxygen supply to the brain to the point that the victim will pass out and *not recover* before suffering irreparable brain damage or death, especially if the victim is already drunk. It's probably impossible from a normal sized balloon, but it used to happen with alarming regularity when breathing from a bottle of He - haven't heard of a case recently so perhaps the addition of O2 has become the standard for "balloon gas." Still, one must assume that any bottle of helium is sans oxygen and treat it accordingly.You cannot die from breathing too much helium or any other inert gas at 1 atm