With helium. In order for a balloon to fly, the sum of the mass of the balloon plus the mass of the air inside the balloon must be less than the mass of the air, and only hydrogen and helium can achieve this condition. There's no hydrogen, so you have to use helium to get the balloon up. Helium is an inert gas that does not burn and does not support combustion, making it safer than hydrogen.
For a balloon to fly, the condition must be that the sum of the mass of the balloon plus the mass of the air inside the balloon is less than the mass of the air
There are two commonly used gases that can achieve this condition: hydrogen and helium.
If you don't have hydrogen, you have to use helium.
Helium is a colorless, odorless rare gas, less dense than air, chemically stable, can not burn, nor combustion-supporting, very safe.
Helium is sold in cans.
How to inflate a balloon with a helium tank:
1. Open the helium valve, put the balloon nozzle on, and lift the nozzle upward to inflate.
2, fill the balloon to reach their desired size, immediately close the valve.
3, pull the tail of the balloon, remember to pinch the air mouth at this time, otherwise the balloon will leak.
4, tie the tail of the balloon with a ribbon, let go of the balloon will fly.