Helium

Allgo Gases helium is used for welding, leak detection and balloon inflation. Colourless, odourless and tasteless, helium is lighter than air and non-flammable. 

For welding, helium is used on materials with a low tolerance for oxidizing elements. The high thermal conductivity makes it preferable to cheaper inerts like Argon where high temperatures and highly conductive metals are used (Aluminium Copper & Magnesium)

Because helium diffuses through solids three times faster than air, it is used as a tracer gas to detect leaks in high-vacuum equipment and high-pressure containers.

With its low density and non-flammable properties, helium is used in airships and balloons to give them lift, welding at height can be facilitated and helium filled party balloons bobbing around on the end of strings  bring colour and delight.