In this particular case, it's carbon dioxide. And that's the process that makes bread rise in the same way as its doming and making the cling film rise here.

在这个特定实验里，这些气体是二氧化碳。而这也是制作面包时以同样的方式形成凸起的过程，就像这个保鲜膜鼓起到了这里。