Leak detecting gases, laser
Nuclear power-plant cooling
Helium was initially used in dirigible-balloons. Nowadays, is used just like argon, in the production of an inert gaseous atmosphere during magnesium, aluminum and titanium welding; it can be used in the cooling of nuclear reactors as transfer media, since it is an inert gas.
Hellium is also used, mixed with oxygen, in asthma treatment because it diffuses very easily through the lungs. It can also be used in respiratory mixtures for high depth divers, because it is less soluble in blood than nitrogen.
In the liquid state, it is used to achieve extremelly low temperatures in electronic devices or for studies in the region of 0-5 K. Hellium is also the adequate gas for low temperature gas thermometers due to its low boiling point and almost ideal behavior.