I was a longtime smoker who quit the old fashioned way, cold turkey. There wasn't all the aids available today when I quit. I can certainly sympathize with folks trying anything to help quit, not easy. As for secondhand smoke, from e-cigs, I would listen to your body. Coughing is a sure sign your bod y is telling you whatever you are breathing is a no-no.
Seems like there are dozens of e-cig manufactures these days, and I am not sure how well regulated the industry is, probably not well, perhaps very little. My instinct is not to trust manufactures of a new trend product that appears to supplant one addiction with another. Even if the new addiction is less harmful than the old. Whatever is in e-cigs is certainly not in the regular air our bodies are meant to breath. So I advise - Step Away from the e-cigs secondhand smoke.
I notice the previous answer gave a link to an article on this site. Here is another article on this site you can checkout http://www.naturalmedicine.com/news/fda-news/fda-issues-warning-to-5-e-cigarette-distributors/. I am sure there are more out there you can find.