Helium is a noble gas, also called inert gas, which does not react with other elements. Therefore, helium balloon gas is not flammable and therefore not explosive.
The main component of balloon gas is always helium. The term "helium" refers to a noble gas with high but varying purity, depending on the field of application. For example, Helium 4.6 has a purity of 99.996% (4 times the number 9, followed by the number 6 = 4.6) and is used for technical and medical purposes. Balloon gas may be of lower purity (minimum 95%), but this does not detract from its use as a filling gas for balloons. Most importatnly, it is of very low weight in comparison to air (about a seventh). We generally recommend (and sell) Balloon gas instead of pure Helium due to the more reasonable price.
Pure helium (e.g. He 4.6) is only harmful if it displaces the oxygen necessary for breathing. In the case of intentional inhalation of pure helium, respiratory and consciousness disturbances or dizziness may arise in addition to the funny high voice. In the case of balloon gas (at least 95% helium), it can not be ruled out with certainty that in addition to helium it contains harmful secondary components, the proportion of which is not shown. For these reasons we feel obliged to warn about the deliberate inhalation of helium or balloon gas.
It is not harmful to inhale small quantities while filling a balloon. Please just do not take deep breaths.
All flying objects are weather depending. It is true, the bigger the balloon, the more lift it has. The more lift it has, the better it stands in the wind. Unfortunately, there is no general rule that you can set up at the desk about which balloon flies up to which wind strength. The difference in gusts is one important aspects. Theoretically, it makes no difference with big balloons if the wind is blowing constantly at 2 wind forces and gusts in wind 6 or it is 0 wind and the gusts have 4 winds.
In addition, the frequency - as in a swing - plays a role. So if it's windy, watch your balloon and secure it if necessary.
100l balloon gas carry about 100gr weight. This means that, for example, a 30 cm balloon with 14 liters of volume displaces 14 liters of air, which weighs about 14 grams. So the balloon has a lift of 14 grams. When filled with the much lighter helium balloon gas, the gas filling weighs almost nothing and the 14g buoyancy is greater than the balloon's own weight (balloon + cord weight). If the buoyancy is not just scarce, but significantly greater than the weight, so the balloon can rise and possibly also carry things.
If the balloon is too small or the balloon is too small (low volume), the buoyancy in relation to the weight may be too low, so that the balloon will not fly in spite of gas filling.
Attention! For safety reasons, do not use gas other than helium balloon gas.