Helium balloons can be described as balloons of any kind which use helium as the principal gas for keeping them in the air. Tethered balloons are the type of balloon that most people imagine when they imagine helium balloons they are the smaller-sized party balloons tied to strings in order to float for decoration.

Helium balloons float in the air due to the fact that the gas inside has a lower density than the air around them. If one gas is heavier than the other, it is likely to rise up over it. It is possible to think of balls floating up in the sky like a plastic bottle filled with air that is in a water pool. 

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Because the air inside the bottle is lighter than water, it will float all the way to the top even if you place it in deep water. Similar to that Helium balloons can float up to the top of the heavier air. How fast the bottle of air rises towards its topmost point is determined by the variation in its densities. This is rather extreme.

Helium balloons aren't able to float in the same way as a bottle of air that is submerged due to the difference in density between air and helium being quite small. Helium balloons weigh very little since they're extremely thin pieces made of plastic. That means even tiny balloons can flounder. As balloons made of helium grow larger they can carry increasing weight. 

As their volume grows more rapidly than their area of the surface if you construct balloons of sufficient size that they are able to transport vehicles and individuals.