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

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