Why doesn't the bubble in a level pop?

Is there some sort of liquid in level that allows the bubble to move around but never pop? Does it have to do with the temperature?

Icant find the answer anywhere!

Thanks. If anyone evens answers this.Why doesn't the bubble in a level pop?
Its not a normal bubble. its just an air pocket that has nowhere to go because its sealed in a little tube. you can make a level "bubble" yourself with a clear straw and some water, just fill the straw almost full of water, hold both ends closed, and hold it horizontal. the "bubble" will move and not pop.Why doesn't the bubble in a level pop?
its a pocket of air in a tube of liquid its not like a soap bubble.