In the current military branches has vaping (e-cigs, e-hookah) been welcomed or frown upon?

I am a avid vaporer now a days moving alway from tobacco products that I got into more while in the service. I had this ask of me one day if vaping has become popular in the service and what type is the most popular. Had to say I didn't know it wasn't around when I was in. Now I am asking you has it bloom in the service or never got a root and if so are there standards to what have as a vaporizer