• Light: Helium has a very low molecular weight of four atomic mass units, which is second only to hydrogen.

• Small size: Helium is one of the smallest molecular compounds of any gas or liquid fluid and can therefore ‘fit’ in places that other molecules cannot, including in the porous voids of some solid materials.

• Chemically inert: As the atomically simplest of the noble gases, helium is the least reactive material known.  No helium-containing compounds have been synthesised.

• Heat transfer: Helium is able to convectively remove heat faster than any other molecular compound.

• Ionisation potential: Helium requires the most amount of energy to ionize (remove) one of its electrons of any molecule. Ionised helium is therefore a highly reactive material.