Yet it takes it weeks or months to leak out (I suppose it'd be more accurate to say 'slip between' the other molecules) of an extremely thin mylar balloon. I am

Yet it takes it weeks or months to leak out (I suppose it'd be more accurate to say 'slip between' the other molecules) of an extremely thin mylar balloon. I am sure it's an engineering challenge to keep it inside a small metal box, but it seems possible, at least. After all, the reserves we have have just been stuck in the ground, without managing to leak into the atmosphere.