An Easier Riddle

It is lighter than a feather, but nobody can hold it for a very long time. What is it? Hint: You don't have to think for a very long time on this one. Just think about things that are lighter than a feather. Like for example, carbon dioxide. That is not the answer, though. But that is close to the answer! So think of synonyms and antonyms to carbon dioxide. This shouldn't be too hard, because I gave you a good hint.