Only helium and hydrogen in the periodic table are lighter than air. So apart from hydrogen and helium, no other gas can make the balloon fly. Hydrogen is a combustible gas, which will burn violently with oxygen in the air in case of fire to generate water. If it is in a balloon, it will explode in case of fire, so there is no hydrogen. Helium is an inert element, which basically does not react with other substances, let alone lighters, so it is called an inert element, so helium is very safe.
In addition, domestic helium is mainly produced by the United States and cartels. At present, due to various factors, the price of helium is rising. Helium is mainly used in scientific research, medical treatment and aerospace fields, because liquid helium has ultra-low temperature properties. As a cryogenic superconducting medium, it requires high purity, generally six nines, that is, 99.9999% purity. Due to the party, there are more and more helium used for ordinary inflatable balloons in China market, but its purity is relatively low, generally 99%.
In addition, don't believe some videos of Tik Tok. It is impossible to inflate a balloon with carbon dioxide. Even the lightest helium has no power. An adult of 1.20kg needs 80,000 helium balloons to float people. Helium has little buoyancy.