In terms of total helium in circulation at any point - this isn't an unreasonable assertion. They use vast quantities of the stuff to keep superconducting magne

In terms of total helium in circulation at any point - this isn't an unreasonable assertion. They use vast quantities of the stuff to keep superconducting magnets and power transmission lines at operational temperatures, and the LHC is far from being the only experiment at CERN.... But on further examination... helium is about 0.1785g/l 1 cubic foot = 28.317 litres So 1 cf. of He has a mass of ~5.05g Cern use 120 metric tons of He in the LHC beam tube magnets alone (http://home.web.cern.ch/about/engineering/cryogenics-low-temperatures-high-performance http://home.web.cern.ch/about/engineering/cryogenics-low-tem... ), so let's say 200 tons at all of CERN, as the beam tube magnets are a pretty major application, and the other accelerators (PS/SPS/etc.) are considerably smaller and slower and have less intensive requirements, and other experiments altogether probably use a fair, but not crazy amount. So... 200 tons of helium equates to 200000000/5.05 = 39.6 million cubic feet, at STP. So, lots and lots of helium, but not 1/3 of the world's supply. Oh, fun fact - that amount of helium would be enough to lift 1100 tonnes of payload from the ground... about two fully laden 747s.