procurement of refilling of gas cylinder procurement of refilling of gas cylinder , co2 , n2 uhp , n2 commercial , o2 medical grade , o2 uhp , mixture co2 5.27%, o2 balance , mixture co2 4.95%, air balance , mixture co2 0.5%, o2 20.47%, n2 balance , mixture o2 5%, co2 5%, nitrogen balance , mixture co2 5%, o2 balance ( 99.99% purity ) , hydrogen uhp , helium special grade 99.999% , helium ( 99.995% ) , zero air grade 1 , argon ( uhp grade ) , ar 95%+h2 5% , ar 90%+h2 10% , n2 95%+h2 5% , n2 90%+h2 10% , sulfur hexafluoride sf6 , nitrous oxide ( n2o ) , acetylene c2h2 ( da ) , p10 ( 10% methane+90 argon )