The primary gas used in balloons is helium. Helium is a colorless, odorless gas that is much lighter than air, allowing balloons filled with helium to float. It is safer than hydrogen, which is flammable, making heliums a preferred choice for party balloons and decorations. Additionally, helium is an inert gas, meaning it does not react easily with other substances, making it suitable for various applications beyond balloons, including scientific research and cooling superconducting magnets. The demand for helium is significant, but its supplies are limited due to its rarity in the Earth's atmosphere.