Not just air-tight, lighter-than-air-tight. I’m not sure if it’s true for the whole set of lighter-than-air gasses, but helium is infamously difficult to keep from leaking, even with modern technology.
Good at making gasses behave is a weird choice for ancient technologies we lost.
Not just air-tight, lighter-than-air-tight. I’m not sure if it’s true for the whole set of lighter-than-air gasses, but helium is infamously difficult to keep from leaking, even with modern technology.
Good at making gasses behave is a weird choice for ancient technologies we lost.
Hydrogen is even worse. It basically moves through solid steel cylinders.