When my arena deck triggers an Unstable Gas, fire quanta is not consumed. Arena deck AI will not attempt to trigger UG without fire quanta present, though.
(http://i1056.photobucket.com/albums/t367/rorrimirrorimage/1_zpsohjsmacw.png)(http://i1056.photobucket.com/albums/t367/rorrimirrorimage/2_zpsjimslvkl.png)
Have not attempted to duplicate with non-upgraded UG.