Radical 84
Radical 84 or radical steam meaning "steam", "air" or "breath" is one of the 34 Kangxi radicals composed of 4 strokes.
In the Kangxi Dictionary, there are 17 characters to be found under this radical.
气 is also the 81st indexing component in the Table of Indexing [Chinese Character Components] predominantly adopted by Simplified Chinese dictionaries published in mainland China.
The radical character is an ancient form of, and used as the simplified form of it in Simplified Chinese.