Though both foil balloons and latex balloons can be filled with helium to float, sometimes your balloon just doesn’t float, even if you blow it up to its full size. The most common reason is that the balloon itself is too small to hold enough helium. Therefore, buoyancy is less than gravity, so it doesn’t seem to float. Choose foil balloons that are over 14 inches and latex balloons that are over 9 inches if you want your balloons to float.

Never fill the balloons with Hydrogen because it is highly inflammable and dangerous, and can cause sudden explosion and harm the passersby in certain temperatures.