The gas commonly used in balloons is helium. Helium is a lightweight, non-toxic, and inert gas that is favored for filling balloons because it is lighter than air, allowing balloons to float. Unlike hydrogen, helium is safe and does not pose a fire hazard, which makes it the preferred choice for many commercial and celebratory applications. Helium-filled balloons are popular at parties, events, and parades. However, helium is a finite resource found in natural gas reserves, raising concerns about its sustainability and availability for future uses.