Helium is a valuable resource. There is precious little of it on Earth. Because it is so light - only hydrogen is lighter - any hydrogen in the atmosphere quickly rises and is soon lost to outer space. Helium is a noble gas and does not form compounds, so cannot be chemically bound (hydrogen is bound in water and organic material, and all fossil fuels). The helium found on Earth is produced as a result of radioactive decay. Radioactive decay often produces alpha particle, the nuclei of helium atoms. Helium can collect in fissures in the Earth, and often above oil deposits. These deposits can be mined and the helium extracted. It is calculated that all the helium on Earth will be extracted and used within a few decades, and we will be reduced to the helium available only during radioactive decay as it happens. Unfortunately, we are not making the best use of the helium we have. Some of it is used in party balloons - obviously not optimal.