They use propane to heat regular air in the balloon.
\The canopy of the balloon only holds heated air, the propane is held in a tank and is only used to create heat.
Helium gas is commonly used in balloons sold by vendors to make them float.
hellium
Helium
Please provide more information/context/clarification to help us answer this question. You can post your response in this answer text by clicking "Edit."
to keep the balloon floating
helium gas
When helium is used to fill a balloon, it expands to fill the space inside the balloon due to its low density. The helium gas takes the shape of the balloon because it moves and distributes evenly throughout the balloon's interior.
The balloon with krypton gas has a higher density than the balloon with argon gas.
propane
When a balloon is squeezed, the volume of the balloon decreases. This causes the gas inside the balloon to be compressed, increasing the pressure of the gas.
This depends on many variables. What is the weight of the notebook, what is the diameter of the balloon, what material is used for the balloon, what gas is used to fill the balloon, what is the weight of the material that is attached to the balloon and the notebook, is this taking place in earth's atmosphere, or somewhere else. There are several other minor variables, as well. And do remember, the balloon must be filled with a gas that is lighter than the surrounding medium!
The gas is hot air.