Tell that to airgas. They intentionally lost a customer who was spending a pretty fair amount of change with them, and they lost that customer by refusing to sell to him for that stated reason.Actually, all commercial helium is of very high purity, because what they sell in cylinders is the boiloff from the liquefaction process. At those temperatures any contaminant has long frozen out and is trivially removed. That's why there is no low-purity, unsuitable for breathing, helium in the market.