The gas typically used when blowing up balloons is helium. Helium is a lighter-than-air gas that provides buoyancy, causing filled balloons to float. It is non-toxic, odorless, and safer than other gases like hydrogen, which is highly flammable. Helium is widely sourced from natural gas reserves and is used not only for balloons but also in various fields, including cryogenics, medicine, and electronics. Its unique properties make helium an essential resource while also contributing to fun at parties and celebrations when used in balloons.