https://www.bocgases.ie/files/balloon_grade_helium_factsheet... says 95% helium and 1% oxygen while https://dan.org/alert-diver/article/helium-gas-purity-what-i... says 97.5% helium but very unlikely for it to be as low as 80%

You sure about that? Everything I've ever heard says that balloon gas is generally grade 4, which is 99.99% pure. Not good enough for MRI, but quite a lot better than 80%.

I believe that that's the stuff you buy in the shop, the non-refillable containers. If you buy a proper refillable balloon gas cylinder it's the higher grade stuff. Source: bought the shop stuff, got disappointed, bought the cylinder, happy.

I can personally attest that this is not foolproof, if it is even the case. Those helium tanks you can buy for large parties knocked me out as a kid. Lost consciousness fell to the ground, blacked out. Supervise your kids if you buy one!

source? the value I found is 97.5%+ helium for party balloons: https://www.grecogas.com/learn-our-industry/your-complete-gu...

People commit suicide with it because it's supposedly painless and quick.

We're dumb enough now to have forgotten history.

Moar hydrogen party balloons. Making partying fun again!

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This is very likely not true.