If you do the same with a real cigarette you will see that the residue is much more toxic, that is why many people prefer to vapear, because at least there are not so many chemicals entering our lungs, and of course, it feels a lot better. That being realistic and having our feet on the ground, we are not 100% sure with the vaping.
There is a new study from 2015 that finds that vaping without nicotine can damage the lungs. I am not a scientist and I am not an alarmist. This report is not a direct study on life and vaping in humans, but it does show an effect.
I tend to take these "studies" with a pinch of salt, as they are often made with an agenda or backed by certain unreliable sources. However, what I am saying is that there is no way that vaping is "safe" at one hundred percent.
There are reports that come out every week with something new and "bad" for the vaping in general. I'm not just trying to scare anyone, I just want you to be informed and aware, you should never be under the impression that vaping is an alternative Safe to smoke, it is not. The only healthy thing for the lungs and health is fresh, clean air. Anything else is going to be at least something unhealthy.